Science.gov

Sample records for imaging principles limitations

  1. PRINCIPLES OF TOMOGRAPHICAL IMAGING WITH LIMITED-ANGLE INPUT

    SciTech Connect

    Tam, K. C.; Perez-Mendez, V.

    1980-09-01

    The theory of tomographical imaging with limited-angular input is discussed , from which two reconstruction algorithms are derived. The existence of missing information due to incomplete angular coverage is demonstrated. and an iteration algorithm to recover this information from a priori knowledge on the finite extent of the object developed. Smoothing algorithms to stabilize reconstructions in the presence of noise are given. The effects of digitization and finite truncation of the reconstruction region in numerical computation are also analysed. It is shown that the limited-angle problem is governed by a set of eigenvalues whose spectrum is determined by the imaging angle and the finite extent of the object. The distortion on a point source caused by the missing information is calculated; from the results some properties of the iteration scheme, such as spatial uniformity, are derived.

  2. Exercise Prescription: Principles and Current Limitations

    PubMed Central

    Shephard, Roy J.

    1983-01-01

    Exercise prescriptions must be both safe and effective, while maximizing patient compliance. Safety can be threatened by physical injury, cardiac emergencies and environmental hazards. Risk can be reduced by individualizing the prescription, although the stress ECG contributes little to the prevention of the exercise catastrophe. Effectiveness of a prescription must be gauged by development of aerobic power and muscular strength, reduction of obesity, improvement of flexibility and control of coronary risk factors. The variability of patient response limits the potential for accurate laboratory prescription of exercise; fine tuning must depend upon the patient's immediate reactions. PMID:21283273

  3. Multi-imager compatible actuation principles in surgical robotics

    PubMed Central

    Stoianovici, D

    2011-01-01

    Today’s most successful surgical robots are perhaps surgeon-driven systems, such as the daVinci (Intuitive Surgical Inc., USA, www.intuitivesurgical.com). These have already enabled surgery that was unattainable with classic instrumentation; however, at their present level of development, they have limited utility. The drawback of these systems is that they are independent self-contained units, and as such, they do not directly take advantage of patient data. The potential of these new surgical tools lies much further ahead. Integration with medical imaging and information are needed for these devices to achieve their true potential. Surgical robots and especially their subclass of image-guided systems require special design, construction and control compared to industrial types, due to the special requirements of the medical and imaging environments. Imager compatibility raises significant engineering challenges for the development of robotic manipulators with respect to imager access, safety, ergonomics, and above all the non-interference with the functionality of the imager. These apply to all known medical imaging types, but are especially challenging for achieving compatibility with the class of MRI systems. Even though a large majority of robotic components may be redesigned to be constructed of MRI compatible materials, for other components such as the motors used in actuation, prescribing MRI compatible materials alone is not sufficient. The electromagnetic motors most commonly used in robotic actuation, for example, are incompatible by principle. As such, alternate actuation principles using “intervention friendly” energy should be adopted and/or devised for these special surgical and radiological interventions. This paper defines the new concept of Multi-imager Compatibility of surgical manipulators and describes its requirements. Subsequently, the paper gives several recommendations and proposes new actuation principles for this concept. Several

  4. Computed tomography imaging and angiography - principles.

    PubMed

    Kamalian, Shervin; Lev, Michael H; Gupta, Rajiv

    2016-01-01

    The evaluation of patients with diverse neurologic disorders was forever changed in the summer of 1973, when the first commercial computed tomography (CT) scanners were introduced. Until then, the detection and characterization of intracranial or spinal lesions could only be inferred by limited spatial resolution radioisotope scans, or by the patterns of tissue and vascular displacement on invasive pneumoencaphalography and direct carotid puncture catheter arteriography. Even the earliest-generation CT scanners - which required tens of minutes for the acquisition and reconstruction of low-resolution images (128×128 matrix) - could, based on density, noninvasively distinguish infarct, hemorrhage, and other mass lesions with unprecedented accuracy. Iodinated, intravenous contrast added further sensitivity and specificity in regions of blood-brain barrier breakdown. The advent of rapid multidetector row CT scanning in the early 1990s created renewed enthusiasm for CT, with CT angiography largely replacing direct catheter angiography. More recently, iterative reconstruction postprocessing techniques have made possible high spatial resolution, reduced noise, very low radiation dose CT scanning. The speed, spatial resolution, contrast resolution, and low radiation dose capability of present-day scanners have also facilitated dual-energy imaging which, like magnetic resonance imaging, for the first time, has allowed tissue-specific CT imaging characterization of intracranial pathology. PMID:27432657

  5. Magnetic resonance imaging: Principles and applications

    SciTech Connect

    Kean, D.; Smith, M.

    1986-01-01

    This text covers the physics underlying magnetic resonance (MR) imaging; pulse sequences; image production; equipment; aspects of clinical imaging; and the imaging of the head and neck, thorax, abdomen and pelvis, and musculoskeletal system; and MR imaging. The book provides about 150 examples of MR images that give an overview of the pathologic conditions imaged. There is a discussion of the physics of MR imaging and also on the spin echo.

  6. Productivity limits and potentials of the principles of conservation agriculture.

    PubMed

    Pittelkow, Cameron M; Liang, Xinqiang; Linquist, Bruce A; van Groenigen, Kees Jan; Lee, Juhwan; Lundy, Mark E; van Gestel, Natasja; Six, Johan; Venterea, Rodney T; van Kessel, Chris

    2015-01-15

    One of the primary challenges of our time is to feed a growing and more demanding world population with reduced external inputs and minimal environmental impacts, all under more variable and extreme climate conditions in the future. Conservation agriculture represents a set of three crop management principles that has received strong international support to help address this challenge, with recent conservation agriculture efforts focusing on smallholder farming systems in sub-Saharan Africa and South Asia. However, conservation agriculture is highly debated, with respect to both its effects on crop yields and its applicability in different farming contexts. Here we conduct a global meta-analysis using 5,463 paired yield observations from 610 studies to compare no-till, the original and central concept of conservation agriculture, with conventional tillage practices across 48 crops and 63 countries. Overall, our results show that no-till reduces yields, yet this response is variable and under certain conditions no-till can produce equivalent or greater yields than conventional tillage. Importantly, when no-till is combined with the other two conservation agriculture principles of residue retention and crop rotation, its negative impacts are minimized. Moreover, no-till in combination with the other two principles significantly increases rainfed crop productivity in dry climates, suggesting that it may become an important climate-change adaptation strategy for ever-drier regions of the world. However, any expansion of conservation agriculture should be done with caution in these areas, as implementation of the other two principles is often challenging in resource-poor and vulnerable smallholder farming systems, thereby increasing the likelihood of yield losses rather than gains. Although farming systems are multifunctional, and environmental and socio-economic factors need to be considered, our analysis indicates that the potential contribution of no-till to the

  7. Principles and Limitations of Ultra-Wideband FM Communications Systems

    NASA Astrophysics Data System (ADS)

    Gerrits, John F. M.; Kouwenhoven, Michiel H. L.; van der Meer, Paul R.; Farserotu, John R.; Long, John R.

    2005-12-01

    This paper presents a novel UWB communications system using double FM: a low-modulation index digital FSK followed by a high-modulation index analog FM to create a constant-envelope UWB signal. FDMA techniques at the subcarrier level are exploited to accommodate multiple users. The system is intended for low (1-10 kbps) and medium (100-1000 kbps) bit rate, and short-range WPAN systems. A wideband delay-line FM demodulator that is not preceded by any limiting amplifier constitutes the key component of the UWBFM receiver. This unusual approach permits multiple users to share the same RF bandwidth. Multipath, however, may limit the useful subcarrier bandwidth to one octave. This paper addresses the performance with AWGN and multipath, the resistance to narrowband interference, as well as the simultaneous detection of multiple FM signals at the same carrier frequency. SPICE and Matlab simulation results illustrate the principles and limitations of this new technology. A hardware demonstrator has been realized and has allowed the confirmation of theory with practical results.

  8. Nuclear cardiac imaging: Principles and applications

    SciTech Connect

    Iskandrian, A.S.

    1986-01-01

    This book provides an analysis of the pathophysiologic concepts and effectiveness of the commonly available cardiac imaging modalities: thallium-201 scintigraphy, myocardial infarct avid-imaging, and radionuclide ventriculography. Emphasis is on the implications of these diagnostic procedures. Organizing an efficient laboratory, instrumentation, radiopharmaceuticals, and exercise testing are discussed.

  9. Basic principles of magnetic resonance imaging.

    PubMed

    Gibby, Wendell A

    2005-01-01

    We have come full circle from spinning quarks to 3D medical images. The bulk of MRI is now performed using slice-selective gradients, during which RF energy is applied to excite the hydrogen nuclei. By stepping a phase-encoding gradient during each TR and using a frequency-encoding gradient as the data are sampled, the 3D human object can be reduced to many individual points or voxels. By acquiring multiple slices at once, the time efficiency of imaging can be vastly improved. Many newer strategies use variations of this technique to acquire multiple lines of data during a single echo, enshrining spin warp imaging as the most important method of signal acquisition for MRI. PMID:15561528

  10. Principles of PET/MR Imaging.

    PubMed

    Disselhorst, Jonathan A; Bezrukov, Ilja; Kolb, Armin; Parl, Christoph; Pichler, Bernd J

    2014-05-12

    Hybrid PET/MR systems have rapidly progressed from the prototype stage to systems that are increasingly being used in the clinics. This review provides an overview of developments in hybrid PET/MR systems and summarizes the current state of the art in PET/MR instrumentation, correction techniques, and data analysis. The strong magnetic field requires considerable changes in the manner by which PET images are acquired and has led, among others, to the development of new PET detectors, such as silicon photomultipliers. During more than a decade of active PET/MR development, several system designs have been described. The technical background of combined PET/MR systems is explained and related challenges are discussed. The necessity for PET attenuation correction required new methods based on MR data. Therefore, an overview of recent developments in this field is provided. Furthermore, MR-based motion correction techniques for PET are discussed, as integrated PET/MR systems provide a platform for measuring motion with high temporal resolution without additional instrumentation. The MR component in PET/MR systems can provide functional information about disease processes or brain function alongside anatomic images. Against this background, we point out new opportunities for data analysis in this new field of multimodal molecular imaging. PMID:24819419

  11. Nonlocal means SAR image despeckling using Principle Neighborhood Dictionaries

    NASA Astrophysics Data System (ADS)

    Zhong, Hua; Yang, Chen; Jiao, L. C.

    2011-11-01

    The Principle Neighborhood Dictionary (PND) filter projects the image patches onto a lower dimensional subspace using Principle Component analysis (PCA), based on which the similarity measure of image patch can be computed with a higher accuracy for the nonlocal means (NLM) algorithm. In this paper, a new PND filter for synthetic aperture radar (SAR) image despeckling is presented, in which a new distance that adapts to the multiplicative speckle noise is derived. Compared with the commonly used Euclidean distance in NLM, the new distance measure improves the accuracy of the similarity measure of speckled patches in SAR images. The proposed method is validated on simulated and real SAR images through comparisons with other classical despeckling methods.

  12. Magnetic Resonance Imaging Part I—Physical Principles

    PubMed Central

    Hendee, William R.; Morgan, Christopher J.

    1984-01-01

    Magnetic resonance (MR) imaging is the most complex imaging technology available to clinicians. Whereas most imaging technologies depict differences in one, or occasionally two, tissue characteristics, MR imaging has five tissue variables—spin density, T1 and T2 relaxation times and flow and spectral shifts—from which to construct its images. These variables can be combined in various ways by selecting pulse sequences and pulse times to emphasize any desired combination of tissue characteristics in the image. This selection is determined by the user of the MR system before imaging data are collected. If the selection is not optimal, the imaging process must be repeated at a cost of time and resources. The optimal selection of MR imaging procedures and the proper interpretation of the resultant images require a thorough understanding of the basic principles of MR imaging. Included in this understanding should be at least the rudiments of how an MR imaging signal is produced and why it decays with time; the significance of relaxation constants; the principles of scanning methods such as saturation recovery, inversion recovery and spin echo; how data obtained by these methods are used to form an image, and how the imaging data are complied by multi-slice and volumetric processes. In selecting an MR imaging unit, information about different magnet designs (resistive, superconductive and permanent) is useful. Although no bioeffects are thought to be associated with an MR imaging examination, some knowledge of the attempts to identify bioeffects is helpful in alleviating concern in patients. Images PMID:6506686

  13. Force Limited Vibration Test of HESSI Imager

    NASA Technical Reports Server (NTRS)

    Amato, Deborah; Pankow, David; Thomsen, Knud

    2000-01-01

    The High Energy Solar Spectroscopic Imager (HESSI) is a solar x-ray and gamma-ray observatory scheduled for launch in November 2000. Vibration testing of the HESSI imager flight unit was performed in August 1999. The HESSI imager consists of a composite metering tube, two aluminum trays mounted to the tube on titanium flexure mounts, and nine modulation grids mounted on each tray. The vibration tests were acceleration controlled and force limited, in order to prevent overtesting. The force limited strategy reduced the shaker force and notched the acceleration at resonances. The test set-up, test levels, and results are presented. The development of the force limits is also discussed. The imager successfully survived the vibration testing.

  14. Coherent imaging at the diffraction limit

    PubMed Central

    Thibault, Pierre; Guizar-Sicairos, Manuel; Menzel, Andreas

    2014-01-01

    X-ray ptychography, a scanning coherent diffractive imaging technique, holds promise for imaging with dose-limited resolution and sensitivity. If the foreseen increase of coherent flux by orders of magnitude can be matched by additional technological and analytical advances, ptychography may approach imaging speeds familiar from full-field methods while retaining its inherently quantitative nature and metrological versatility. Beyond promises of high throughput, spectroscopic applications in three dimensions become feasible, as do measurements of sample dynamics through time-resolved imaging or careful characterization of decoherence effects. PMID:25177990

  15. Large aperture spatial heterodyne imaging spectrometer: Principle and experimental results

    NASA Astrophysics Data System (ADS)

    Xiangli, Bin; Cai, Qisheng; Du, Shusong

    2015-12-01

    A large aperture spatial heterodyne imaging spectrometer (LASHIS) is proposed. It is a kind of pushbroom Fourier transform ultraspectral imager with no moving parts. This imaging spectrometer, based on a Sagnac lateral shearing interferometer combined with a pair of gratings, has the advantages of high spectral resolution, high throughput and robustness. The principle of LASHIS and its spectral retrieval method are introduced. The processing chain to convert raw images to ultraspectral datacube is also described. Experimental results demonstrate the high resolving power of LASHIS with the emission spectrum of a low pressure sodium lamp.

  16. Electron-optic limitations on image resolution

    NASA Technical Reports Server (NTRS)

    Engstrom, R. W.

    1973-01-01

    Various approaches are considered to the solution of the electron-optical problem of designing an image tube configuration. Emphasis is placed on the method of computer design, and an illustration is given in which the technique is used in the design of an 80-mm image tube with a zoom capability of 3:1. The solutions are discussed to such problems as image distortion, magnification, and electron bundles striking the zoom electrode. Three types of an electron-optical configuration are examined for the electron-optic limitations to resolution: (1) the proximity image tube, (2) the magnetic-type image tube having uniform electric and magnetic fields, and (3) the electrostatic-type image tube such as the 80-mm zoom tube.

  17. Cosmological equivalence principle and the weak-field limit

    SciTech Connect

    Wiltshire, David L.

    2008-10-15

    The strong equivalence principle is extended in application to averaged dynamical fields in cosmology to include the role of the average density in the determination of inertial frames. The resulting cosmological equivalence principle is applied to the problem of synchronization of clocks in the observed universe. Once density perturbations grow to give density contrasts of order 1 on scales of tens of megaparsecs, the integrated deceleration of the local background regions of voids relative to galaxies must be accounted for in the relative synchronization of clocks of ideal observers who measure an isotropic cosmic microwave background. The relative deceleration of the background can be expected to represent a scale in which weak-field Newtonian dynamics should be modified to account for dynamical gradients in the Ricci scalar curvature of space. This acceleration scale is estimated using the best-fit nonlinear bubble model of the universe with backreaction. At redshifts z < or approx. 0.25 the scale is found to coincide with the empirical acceleration scale of modified Newtonian dynamics. At larger redshifts the scale varies in a manner which is likely to be important for understanding dynamics of galaxy clusters, and structure formation. Although the relative deceleration, typically of order 10{sup -10} ms{sup -2}, is small, when integrated over the lifetime of the universe it amounts to an accumulated relative difference of 38% in the rate of average clocks in galaxies as compared to volume-average clocks in the emptiness of voids. A number of foundational aspects of the cosmological equivalence principle are also discussed, including its relation to Mach's principle, the Weyl curvature hypothesis, and the initial conditions of the universe.

  18. Uncertainty Principle--Limited Experiments: Fact or Academic Pipe-Dream?

    ERIC Educational Resources Information Center

    Albergotti, J. Clifton

    1973-01-01

    The question of whether modern experiments are limited by the uncertainty principle or by the instruments used to perform the experiments is discussed. Several key experiments show that the instruments limit our knowledge and the principle remains of strictly academic concern. (DF)

  19. Fermat's principle, caustics, and the classification of gravitational lens images

    SciTech Connect

    Blandford, R.; Narayan, R.

    1986-11-01

    A scalar description of gravitational lensing based on Fermat's principle is described. The lensing mass is assumed to be confined to a single plane between the source and the observer, and a time delay is associated with each position in the sky of a potential image. The extrema of this time surface then give the true positions of the images. A topological classification of image configurations is presented, and the results are generalized to cases of three and five-image lensing geometries. A computer-graphical approach to the study of lensing by model galaxies and clusters is described, and the design of a simple optical apparatus which could be used for fast modelling of image geometries is outlined. The connection between the Fermat approach and the classical theory of caustics and the more recent general theory of catastrophies is developed. The extension of the results to multiple scattering is considered. 42 references.

  20. On the Diffraction Limit for Lensless Imaging

    PubMed Central

    Mielenz, Klaus D.

    1999-01-01

    The diffraction limit for lensless imaging, defined as the sharpest possible point image obtainable with a pinhole aperture, is analyzed and compared to the corresponding limit for imaging with lenses by means of theoretical considerations and numerical computations using the Fresnel-Lommel diffraction theory for circular apertures. The numerical result (u = π) obtained for the best configuration parameter u which defines the optical setup is consistent with the quarter-wave criterion, and is the same as the value reported in a classical paper by Petzval but smaller than the value (u = 1.8π) found by Lord Rayleigh. The smallest discernible detail (pixel) in a composite image is defined by an expression found by Rayleigh on applying the half-wave criterion and is shown to be consistent with the Sparrow criterion of resolution. The numerical values of other measures of image size are reported and compared to equivalent parameters of the Fraunhofer-Airy profile that governs imaging with lenses.

  1. STRIPE: Remote Driving Using Limited Image Data

    NASA Technical Reports Server (NTRS)

    Kay, Jennifer S.

    1997-01-01

    Driving a vehicle, either directly or remotely, is an inherently visual task. When heavy fog limits visibility, we reduce our car's speed to a slow crawl, even along very familiar roads. In teleoperation systems, an operator's view is limited to images provided by one or more cameras mounted on the remote vehicle. Traditional methods of vehicle teleoperation require that a real time stream of images is transmitted from the vehicle camera to the operator control station, and the operator steers the vehicle accordingly. For this type of teleoperation, the transmission link between the vehicle and operator workstation must be very high bandwidth (because of the high volume of images required) and very low latency (because delayed images can cause operators to steer incorrectly). In many situations, such a high-bandwidth, low-latency communication link is unavailable or even technically impossible to provide. Supervised TeleRobotics using Incremental Polyhedral Earth geometry, or STRIPE, is a teleoperation system for a robot vehicle that allows a human operator to accurately control the remote vehicle across very low bandwidth communication links, and communication links with large delays. In STRIPE, a single image from a camera mounted on the vehicle is transmitted to the operator workstation. The operator uses a mouse to pick a series of 'waypoints' in the image that define a path that the vehicle should follow. These 2D waypoints are then transmitted back to the vehicle, where they are used to compute the appropriate steering commands while the next image is being transmitted. STRIPE requires no advance knowledge of the terrain to be traversed, and can be used by novice operators with only minimal training. STRIPE is a unique combination of computer and human control. The computer must determine the 3D world path designated by the 2D waypoints and then accurately control the vehicle over rugged terrain. The human issues involve accurate path selection, and the

  2. Correction of geometric and refractive image distortions in optical coherence tomography applying Fermat's principle.

    PubMed

    Westphal, Volker; Rollins, Andrew; Radhakrishnan, Sunita; Izatt, Joseph

    2002-05-01

    We describe a methodology for quantitative image correction in OCT which includes procedures for correction of nonlinear axial scanning and non-telecentric scan patterns, as well as a novel approach for refraction correction in layered media based on Fermat's principle. The residual spatial error obtained in layered media with a fan-beam hand-held probe was reduced from several hundred micrometers to near the diffraction and coherence-length limits. PMID:19436373

  3. Working with images: applying writing principles to photography

    SciTech Connect

    Silverstein, A.P.

    1982-01-05

    Photography and writing are two media with the power to communicate. Both use a language: photogrphy uses images, writing uses words. Recognizing this similarity can help the writer/editor who knows very little about photography. If you regard a photography assignment in the same light as a writing assignment, you can apply the general principles of writing to photography. For instance, before you begin to create in any medium you need to consider your audience, your purpose, and your format. Next, you need to get to know your equipment, overcome your anxieties, and get started (often the most difficult step of the whole process). As you create and while you edit, remember these simple rules which hold true for words and images: Keep it clear and simple, beware of jargon, and choose the active voice.

  4. Detection limits with spectral differential imaging data

    NASA Astrophysics Data System (ADS)

    Rameau, J.; Chauvin, G.; Lagrange, A.-M.; Maire, A.-L.; Boccaletti, A.; Bonnefoy, M.

    2015-09-01

    Context. Direct imaging of exoplanets is polluted by speckle noise that severely limits the achievable contrast. Angular and spectral differential imaging have been proposed to make use of the temporal and chromatic properties of the speckles. Both modes, associated with extreme adaptive-optics and coronagraphy, are at the core of the new generation of planet imagers SPHERE and GPI. Aims: We aim to illustrate and characterize the impact of the SDI and SDI+ADI (ASDI) data reduction on the detection of giant planets. We also propose an unbiased method to derive the detection limits from SDI/ASDI data. Methods: Observations of AB Dor B and β Pictoris made with VLT/NaCo were used to simulate and quantify the effects of SDI and ASDI. The novel method is compared to the traditional injection of artificial point sources. Results: The SDI reduction process creates a typical radial positive-negative pattern of any point-source. Its characteristics and its self-subtraction depend on the separation, but also on the spectral properties of the object. This work demonstrates that the self-subtraction cannot be reduced to a simple geometric effect. As a consequence, the detection performances of SDI observations cannot be expressed as a contrast in magnitude with the central star without the knowledge of the spectral properties of detectable companions. In addition, the residual noise cannot be converted into contrast and physical characteristics (mass, temperature) by standard calibration of flux losses. The proposed method takes the SDI bias into account to derive detection limits without the cost of massively injecting artificial sources into the data. Finally, the sensitivity of ASDI observations can be measured only with a control parameter on the algorithms that controls the minimum rotation that is necessary to build the reference image. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, ESO : 60.A

  5. Resolution limits in imaging LADAR systems

    NASA Astrophysics Data System (ADS)

    Khoury, Jed; Woods, Charles L.; Lorenzo, Joseph P.; Kierstead, John; Pyburn, Dana; Sengupta, S. K.

    2004-04-01

    In this paper, we introduce a new design concept of laser radar systems that combines both phase comparison and time-of-flight methods. We show from signal to noise ration considerations that there is a fundamental limit to the overall resolution in 3-D imaging range laser radar (LADAR). We introduce a new metric, volume of resolution (VOR), and we show from quantum noise considerations, that there is a maximum resolution volume, that can be achieved, for a given set of system parameters. Consequently, there is a direct tradeoff between range resolution and spatial resolution. Thus in a LADAR system, range resolution may be maximized at the expense of spatial image resolution and vice versa. We introduce resolution efficiency, ηr, as a new figure of merit for LADAR, that describes system resolution under the constraints of a specific design, compared to its optimal resolution performance derived from quantum noise considerations. We analyze how the resolution efficiency could be utilized to improve the resolution performance of a LADAR system. Our analysis could be extended to all LADAR systems, regardless of whether they are flash imaging or scanning laser systems.

  6. The Galilean Relativity Principle as Non-Relativistic Limit of EINSTEIN'S One in Extended Thermodynamics

    NASA Astrophysics Data System (ADS)

    Pennisi, S.; Carrisi, M. C.; Scanu, A.

    2006-03-01

    It is well known that, in the relativistic context the relativity principle isn't imposed by separating variables into convective and non convective parts, but by imposing that the costitutive functions satisfy particular conditions; likely to this, the present considerations show that the same results are obtained also in the classical context. The result is achieved by taking the non-relativistic limit of Einstein's Relativity Principle. This fact furnishes further arguments on the naturalness of the work “A new method to exploit the Entropy Principle and Galilean invariance in the macroscopic approach of Extended Thermodynamics” by Pennisi and Ruggeri.

  7. Principles of functional magnetic resonance imaging: application to auditory neuroscience.

    PubMed

    Cacace, A T; Tasciyan, T; Cousins, J P

    2000-05-01

    Functional imaging based on magnetic resonance methods is a new research frontier for exploring a wide range of central nervous system (CNS) functions, including information processing in sensory, motor, cognitive, and linguistic systems. Being able to localize and study human brain function in vivo, in relatively high resolution and in a noninvasive manner, makes this a technique of unparalleled importance. In order to appreciate and fully understand this area of investigation, a tutorial covering basic aspects of this methodology is presented. We introduce functional magnetic resonance imaging (fMRI) by providing an overview of the studies of different sensory systems in response to modality-specific stimuli, followed by an outline of other areas that have potential clinical relevance to the medical, cognitive, and communicative sciences. The discussion then focuses on the basic principles of magnetic resonance methods including magnetic resonance imaging, MR spectroscopy, fMRI, and the potential role that MR technology may play in understanding a wide range of auditory functions within the CNS, including tinnitus-related activity. Because the content of the material found herein might be unfamiliar to some, we provide a broad range of background and review articles to serve as a technical resource. PMID:10821504

  8. The Global Landscape of Occupational Exposure Limits--Implementation of Harmonization Principles to Guide Limit Selection.

    PubMed

    Deveau, M; Chen, C-P; Johanson, G; Krewski, D; Maier, A; Niven, K J; Ripple, S; Schulte, P A; Silk, J; Urbanus, J H; Zalk, D M; Niemeier, R W

    2015-01-01

    Occupational exposure limits (OELs) serve as health-based benchmarks against which measured or estimated workplace exposures can be compared. In the years since the introduction of OELs to public health practice, both developed and developing countries have established processes for deriving, setting, and using OELs to protect workers exposed to hazardous chemicals. These processes vary widely, however, and have thus resulted in a confusing international landscape for identifying and applying such limits in workplaces. The occupational hygienist will encounter significant overlap in coverage among organizations for many chemicals, while other important chemicals have OELs developed by few, if any, organizations. Where multiple organizations have published an OEL, the derived value often varies considerably-reflecting differences in both risk policy and risk assessment methodology as well as access to available pertinent data. This article explores the underlying reasons for variability in OELs, and recommends the harmonization of risk-based methods used by OEL-deriving organizations. A framework is also proposed for the identification and systematic evaluation of OEL resources, which occupational hygienists can use to support risk characterization and risk management decisions in situations where multiple potentially relevant OELs exist. PMID:26099071

  9. Molecular Body Imaging: MR Imaging, CT, and US. Part I. Principles

    PubMed Central

    Kircher, Moritz F.

    2012-01-01

    Molecular imaging, generally defined as noninvasive imaging of cellular and subcellular events, has gained tremendous depth and breadth as a research and clinical discipline in recent years. The coalescence of major advances in engineering, molecular biology, chemistry, immunology, and genetics has fueled multi- and interdisciplinary innovations with the goal of driving clinical noninvasive imaging strategies that will ultimately allow disease identification, risk stratification, and monitoring of therapy effects with unparalleled sensitivity and specificity. Techniques that allow imaging of molecular and cellular events facilitate and go hand in hand with the development of molecular therapies, offering promise for successfully combining imaging with therapy. While traditionally nuclear medicine imaging techniques, in particular positron emission tomography (PET), PET combined with computed tomography (CT), and single photon emission computed tomography, have been the molecular imaging methods most familiar to clinicians, great advances have recently been made in developing imaging techniques that utilize magnetic resonance (MR), optical, CT, and ultrasonographic (US) imaging. In the first part of this review series, we present an overview of the principles of MR imaging-, CT-, and US-based molecular imaging strategies. © RSNA, 2012 PMID:22623690

  10. Development of design principles for a creep-limited alloy for turbine blades

    NASA Astrophysics Data System (ADS)

    Huda, Z.

    1995-02-01

    Recent advancements in turbine-blade materials engineering are reviewed in light of general superalloy research and the author’s work on a new powder metallurgy IN-792 creep-limited alloy for application in blades of gas-turbine engines. The developed set of principles presented in this paper incorporates all the factors that must be taken into consideration in selecting and designing an alloy for turbine blades.

  11. The Uncertainty Threshold Principle: Some Fundamental Limitations of Optimal Decision Making Under Dynamic Uncertainity

    NASA Technical Reports Server (NTRS)

    Athans, M.; Ku, R.; Gershwin, S. B.

    1977-01-01

    This note shows that the optimal control of dynamic systems with uncertain parameters has certain limitations. In particular, by means of a simple scalar linear-quadratic optimal control example, it is shown that the infinite horizon solution does not exist if the parameter uncertainty exceeds a certain quantifiable threshold; we call this the uncertainty threshold principle. The philosophical and design implications of this result are discussed.

  12. The uncertainty threshold principle - Some fundamental limitations of optimal decision making under dynamic uncertainty

    NASA Technical Reports Server (NTRS)

    Athans, M.; Ku, R.; Gershwin, S. B.

    1977-01-01

    This note shows that the optimal control of dynamic systems with uncertain parameters has certain limitations. In particular, by means of a simple scalar linear-quadratic optimal control example, it is shown that the infinite horizon solution does not exist if the parameter uncertainty exceeds a certain quantifiable threshold; we call this the uncertainty threshold principle. The philosophical and design implications of this result are discussed.

  13. [Digital thoracic radiology: devices, image processing, limits].

    PubMed

    Frija, J; de Géry, S; Lallouet, F; Guermazi, A; Zagdanski, A M; De Kerviler, E

    2001-09-01

    In a first part, the different techniques of digital thoracic radiography are described. Since computed radiography with phosphore plates are the most commercialized it is more emphasized. But the other detectors are also described, as the drum coated with selenium and the direct digital radiography with selenium detectors. The other detectors are also studied in particular indirect flat panels detectors and the system with four high resolution CCD cameras. In a second step the most important image processing are discussed: the gradation curves, the unsharp mask processing, the system MUSICA, the dynamic range compression or reduction, the soustraction with dual energy. In the last part the advantages and the drawbacks of computed thoracic radiography are emphasized. The most important are the almost constant good quality of the pictures and the possibilities of image processing. PMID:11567193

  14. Limiting liability via high resolution image processing

    SciTech Connect

    Greenwade, L.E.; Overlin, T.K.

    1996-12-31

    The utilization of high resolution image processing allows forensic analysts and visualization scientists to assist detectives by enhancing field photographs, and by providing the tools and training to increase the quality and usability of field photos. Through the use of digitized photographs and computerized enhancement software, field evidence can be obtained and processed as `evidence ready`, even in poor lighting and shadowed conditions or darkened rooms. These images, which are most often unusable when taken with standard camera equipment, can be shot in the worst of photographic condition and be processed as usable evidence. Visualization scientists have taken the use of digital photographic image processing and moved the process of crime scene photos into the technology age. The use of high resolution technology will assist law enforcement in making better use of crime scene photography and positive identification of prints. Valuable court room and investigation time can be saved and better served by this accurate, performance based process. Inconclusive evidence does not lead to convictions. Enhancement of the photographic capability helps solve one major problem with crime scene photos, that if taken with standard equipment and without the benefit of enhancement software would be inconclusive, thus allowing guilty parties to be set free due to lack of evidence.

  15. Microscope and spectroscope results are not limited by Heisenberg's Uncertainty Principle!

    NASA Astrophysics Data System (ADS)

    Prasad, Narasimha S.; Roychoudhuri, Chandrasekhar

    2011-09-01

    A reviewing of many published experimental and theoretical papers demonstrate that the resolving powers of microscopes, spectroscopes and telescopes can be enhanced by orders of magnitude better than old classical limits by various advanced techniques including de-convolution of the CW-response function of these instruments. Heisenberg's original analogy of limited resolution of a microscope, to support his mathematical uncertainty relation, is no longer justifiable today. Modern techniques of detecting single isolated atoms through fluorescence also over-ride this generalized uncertainty principle. Various nano-technology techniques are also making atoms observable and location precisely measurable. Even the traditional time-frequency uncertainty relation or bandwidth limit δvδt >= 1 can be circumvented while doing spectrometry with short pulses by deriving and de-convolving the pulse-response function of the spectrometer just as we do for CW input.

  16. From general policy to legal rule: aspirations and limitations of the precautionary principle.

    PubMed Central

    Marchant, Gary E

    2003-01-01

    The rapid spread of the precautionary principle (PP) demonstrates the need to explicitly address the role of precaution in environmental decision making. Unfortunately, the PP in its current form is limited by the vagueness of, and variations in, the many formulations of the PP. This ambiguity in the meaning of the PP would not be so serious if the PP were limited to a general aspirational policy, but in every jurisdiction that has adopted the PP it has been transformed rapidly into a binding legal rule. As a legal rule, the ambiguity of the PP results in arbitrary application by regulatory agencies and reviewing courts and limits the capability of reviewing courts to perform their function in overseeing agency actions. To improve the explicit application of precaution, we must go beyond the current form of the PP and attempt to define the factors that weigh in favor of more or less precaution for specific risks. PMID:14594635

  17. The superluminal limit as a consequence of the classical causality principle

    NASA Astrophysics Data System (ADS)

    Cutolo, A.

    2012-01-01

    The superluminal limit states that no physical object can overpass the velocity of the light in vacuum. This limit is usually considered a consequence of the special theory of relativity (STR). In contrast with the basic hypotheses chosen by Albert Einstein, many authors wrongly consider it a basic assumption of the STR. Here, we revise this limit by showing that it can be derived as a consequence of the classical causality principle without invoking any additional hypotheses. It will be demonstrated to hold true in any kind of medium even in those exhibiting either a phase or group velocity of the light greater than that of light in vacuum. The behavior of some neutral particles ( e.g. neutrinos, photons) is shown to be fully consistent with this model. The validity of our discussion rests on the hypotheses of a gravitationless vacuum.

  18. Limits on Einstein’s Equivalence Principle from the First Localized Fast Radio Burst FRB 150418

    NASA Astrophysics Data System (ADS)

    Tingay, S. J.; Kaplan, D. L.

    2016-04-01

    Fast radio bursts (FRBs) have recently been used to place limits on Einstein's Equivalence Principle via observations of time delays between photons of different radio frequencies by Wei et al. These limits on differential post-Newtonian parameters ({{Δ }}γ \\lt 2.52× {10}-8) are the best yet achieved, but they still rely on uncertain assumptions, namely the relative contributions of dispersion and gravitational delays to the observed time delays and the distances to FRBs. Also, very recently, the first FRB host galaxy has likely been identified, providing the first redshift-based distance estimate to FRB 150418. Moreover, consistency between the {{{Ω }}}{{IGM}} estimate from FRB 150418 and {{{Ω }}}{{IGM}}, expected from ΛCDM models and WMAP observations, leads one to conclude that the observed time delay for FRB 150418 is highly dominated by dispersion, with any gravitational delays being small contributors. This points to even tighter limits on Δγ. In this paper, the technique of Wei et al. is applied to FRB 150418 to produce a limit of Δγ < 1-2 × 10-9, approximately an order of magnitude better than previous limits and in line with expectations by Wei et al. for what could be achieved if the dispersive delay is separated from other effects. Future substantial improvements in such limits will depend on accurately determining the contribution of individual ionized components to the total observed time delays for FRBs.

  19. The uncertainty threshold principle - Fundamental limitations of optimal decision making under dynamic uncertainty

    NASA Technical Reports Server (NTRS)

    Athans, M.; Ku, R.; Gershwin, S. B.

    1976-01-01

    The fundamental limitations of the optimal control of dynamic systems with random parameters are analyzed by studying a scalar linear-quadratic optimal control example. It is demonstrated that optimum long-range decision making is possible only if the dynamic uncertainty (quantified by the means and covariances of the random parameters) is below a certain threshold. If this threshold is exceeded, there do not exist optimum decision rules. This phenomenon is called the 'uncertainty threshold principle'. The implications of this phenomenon to the field of modelling, identification, and adaptive control are discussed.

  20. Nonrelativistic limit of quantum field theory in inertial and noninertial frames and the principle of equivalence

    SciTech Connect

    Padmanabhan, Hamsa; Padmanabhan, T.

    2011-10-15

    We discuss the nonrelativistic limit of quantum field theory in an inertial frame, in the Rindler frame and in the presence of a weak gravitational field, and attempt to highlight and clarify several subtleties. In particular, we study the following issues: (a) While the action for a relativistic free particle is invariant under the Lorentz transformation, the corresponding action for a nonrelativistic free particle is not invariant under the Galilean transformation, but picks up extra contributions at the end points. This leads to an extra phase in the nonrelativistic wave function under a Galilean transformation, which can be related to the rest energy of the particle even in the nonrelativistic limit. We show that this is closely related to the peculiar fact that the relativistic action for a free particle remains invariant even if we restrict ourselves to O(1/c{sup 2}) in implementing the Lorentz transformation. (b) We provide a brief critique of the principle of equivalence in the quantum mechanical context. In particular, we show how solutions to the generally covariant Klein-Gordon equation in a noninertial frame, which has a time-dependent acceleration, reduce to the nonrelativistic wave function in the presence of an appropriate (time-dependent) gravitational field in the c{yields}{infinity} limit, and relate this fact to the validity of the principle of equivalence in a quantum mechanical context. We also show that the extra phase acquired by the nonrelativistic wave function in an accelerated frame, actually arises from the gravitational time dilation and survives in the nonrelativistic limit. (c) While the solution of the Schroedinger equation can be given an interpretation as being the probability amplitude for a single particle, such an interpretation fails in quantum field theory. We show how, in spite of this, one can explicitly evaluate the path integral using the (nonquadratic) action for a relativistic particle (involving a square root) and

  1. Miniaturized power limiter metasurface based on Fano-type resonance and Babinet principle.

    PubMed

    Loo, Y L; Wang, H G; Zhang, H; Ong, C K

    2016-09-01

    In this work, we present a miniaturize power limiter, a device with size smaller than that required by the working frequency, made of coupled self-complementary electric inductive-capacitive (CELC) resonator and original electric inductive-capacitive (ELC) structure. We also make use of Babinet principle to ensure both CELC and ELC are resonating at the same frequency. The CELC structure is loaded with a Schottky diode to achieve the effect of a nonlinear power limiter. The constructive interference of CELC and ELC structure produces a new Fano-type resonance peak at a lower frequency. The Fano peak is sharp and able to concentrate electric field at a region between the inner and outer metallic patch of the metastructure, hence enhancing the nonlinear properties of the loaded diode. The Fano peak enhances the maximum isolation of the power limiter due to the local field enhancement at where the diode is loaded. Numerical simulation and experiment are conducted in the S-band frequency to verify the power limiting effect of the device designed and to discuss the formation of Fano peak. The power limiter designed has a maximum isolation of 8.4 dB and a 3-dB isolation bandwidth of 6%. PMID:27607685

  2. Statistical Characterization of Radiological Images: Basic Principles and Recent Progress

    PubMed Central

    Barrett, Harrison H.; Myers, Kyle J.

    2010-01-01

    This paper surveys our current understanding of the statistical properties of radiological images and their effect on image quality. Attention is given to statistical descriptions needed to compute the performance of ideal or ideal-linear observers on detection and estimation tasks. The effects of measurement noise, random objects and random imaging system are analyzed by nested conditional averaging, leading to a three-term expansion of the data covariance matrix. Characteristic functionals are introduced to account for the object statistics, and it is shown how they can be used to compute the image statistics. PMID:20948984

  3. Pitfalls and Limitations of Radionuclide Imaging in Endocrinology.

    PubMed

    Agrawal, Kanhaiyalal; Esmail, Abdulredha A H; Gnanasegaran, Gopinath; Navalkissoor, Shaunak; Mittal, Bhagwant Rai; Fogelman, Ignac

    2015-09-01

    Several different techniques, radiopharmaceuticals, and imaging modalities are commonly used in nuclear medicine for studies of endocrine organs. Nuclear medicine is used in the management of benign and malignant thyroid, parathyroid, and neuroendocrine disorders. Thus, it is essential to acknowledge pitfalls and the limitations of nuclear medicine imaging for accurate diagnosis and patient management. PMID:26278855

  4. Imaging genomics in cancer research: limitations and promises.

    PubMed

    Bai, Harrison X; Lee, Ashley M; Yang, Li; Zhang, Paul; Davatzikos, Christos; Maris, John M; Diskin, Sharon J

    2016-05-01

    Recently, radiogenomics or imaging genomics has emerged as a novel high-throughput method of associating imaging features with genomic data. Radiogenomics has the potential to provide comprehensive intratumour, intertumour and peritumour information non-invasively. This review article summarizes the current state of radiogenomic research in tumour characterization, discusses some of its limitations and promises and projects its future directions. Semi-radiogenomic studies that relate specific gene expressions to imaging features will also be briefly reviewed. PMID:26864054

  5. The Basic Principles of FDG-PET/CT Imaging.

    PubMed

    Basu, Sandip; Hess, Søren; Nielsen Braad, Poul-Erik; Olsen, Birgitte Brinkmann; Inglev, Signe; Høilund-Carlsen, Poul Flemming

    2014-10-01

    Positron emission tomography (PET) imaging with 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) forms the basis of molecular imaging. FDG-PET imaging is a multidisciplinary undertaking that requires close interdisciplinary collaboration in a broad team comprising physicians, technologists, secretaries, radio-chemists, hospital physicists, molecular biologists, engineers, and cyclotron technicians. The aim of this review is to provide a brief overview of important basic issues and considerations pivotal to successful patient examinations, including basic physics, instrumentation, radiochemistry, molecular and cell biology, patient preparation, normal distribution of tracer, and potential interpretive pitfalls. PMID:26050942

  6. Basic principles of magnetic resonance imaging--an update.

    PubMed

    Scherzinger, A L; Hendee, W R

    1985-12-01

    Magnetic resonance (MR) imaging technology has undergone many technologic advances over the past few years. Many of these advances were stimulated by the wealth of information emerging from nuclear magnetic resonance research in the areas of new and optimal scanning methods and radio-frequency coil design. Other changes arose from the desire to improve image quality, ease siting restrictions and generally facilitate the clinical use of MR equipment. Many questions, however, remain unanswered. Perhaps the most controversial technologic question involves the optimal field strength required for imaging or spectroscopic applications or both. Other issues include safety and clinical efficacy. Technologic issues affect all aspects of MR use including the choice of equipment, examination procedure and image interpretation. Thus, an understanding of recent changes and their theoretic basis is necessary. PMID:3911591

  7. Expanded solar-system limits on violations of the equivalence principle

    NASA Astrophysics Data System (ADS)

    Overduin, James; Mitcham, Jack; Warecki, Zoey

    2014-01-01

    Most attempts to unify general relativity with the standard model of particle physics predict violations of the equivalence principle associated in some way with the composition of the test masses. We test this idea by using observational uncertainties in the positions and motions of solar-system bodies to set upper limits on the relative difference Δ between gravitational and inertial mass for each body. For suitable pairs of objects, it is possible to constrain three different linear combinations of Δ using Kepler’s third law, the migration of stable Lagrange points, and orbital polarization (the Nordtvedt effect). Limits of order 10-10-10-6 on Δ for individual bodies can then be derived from planetary and lunar ephemerides, Cassini observations of the Saturn system, and observations of Jupiter’s Trojan asteroids as well as recently discovered Trojan companions around the Earth, Mars, Neptune, and Saturnian moons. These results can be combined with models for elemental abundances in each body to test for composition-dependent violations of the universality of free fall in the solar system. The resulting limits are weaker than those from laboratory experiments, but span a larger volume in composition space.

  8. Quantitative characterization of the limiting resolution of a microscanning imager.

    PubMed

    Wang, Xiao-Rui; Zhang, Jian-Qi

    2006-08-01

    A method to determine the limiting resolution of a microscanning imager is proposed. Specifically, both the sample-scene phase effects and aliasing effects due to microscanning are modeled in this method by combining the pixel transfer function and the squeeze modulation transfer function. Further, this model is used to calculate the amount of improvement from typical microscanning modes to the limiting resolution of the imager focusing on various blur factors. Analytical results show that the limiting resolution of the microscanning imager is closely related to microscanning modes. The amount of improvement from different microscanning modes to the limiting resolution is different and is closely associated with the fill factor and the blur factors. The conclusion obtained will be helpful in choosing the optimum microscanning mode according to the fill factor of the detector and system blur factors. PMID:16835642

  9. Abstracting the principles of development using imaging and modeling

    PubMed Central

    Xiong, Fengzhu; Megason, Sean G.

    2015-01-01

    Summary Here we look at modern developmental biology with a focus on the relationship between different approaches of investigation. We argue that direct imaging is a powerful approach not only for obtaining descriptive information but also for model generation and testing that lead to mechanistic insights. Modeling, on the other hand, conceptualizes imaging data and provides guidance to perturbations. The inquiry progresses most efficiently when a trinity of approaches—quantitative imaging (measurement), modeling (theory) and perturbation (test) —are pursued in concert, but not when one approach is dominant. Using recent studies of the zebrafish system, we show how this combination has effectively advanced classic topics in developmental biology compared to a perturbation-centric approach. Finally, we show that interdisciplinary expertise and perhaps specialization are necessary for carrying out a systematic approach, and discuss the technical hurdles. PMID:25946995

  10. Image force microscopy of molecular resonance: A microscope principle

    PubMed Central

    Rajapaksa, I.; Uenal, K.; Wickramasinghe, H. Kumar

    2010-01-01

    We demonstrate a technique in microscopy which extends the domain of atomic force microscopy to optical spectroscopy at the nanometer scale. We show that molecular resonance of feature sizes down to the single molecular level can be detected and imaged purely by mechanical detection of the force gradient between the interaction of the optically driven molecular dipole and its mirror image in a platinum coated scanning probe tip. This microscopy and spectroscopy technique is extendable to frequencies ranging from radio to infrared and the ultraviolet. PMID:20859536

  11. Learning to rank image tags with limited training examples.

    PubMed

    Songhe Feng; Zheyun Feng; Rong Jin

    2015-04-01

    With an increasing number of images that are available in social media, image annotation has emerged as an important research topic due to its application in image matching and retrieval. Most studies cast image annotation into a multilabel classification problem. The main shortcoming of this approach is that it requires a large number of training images with clean and complete annotations in order to learn a reliable model for tag prediction. We address this limitation by developing a novel approach that combines the strength of tag ranking with the power of matrix recovery. Instead of having to make a binary decision for each tag, our approach ranks tags in the descending order of their relevance to the given image, significantly simplifying the problem. In addition, the proposed method aggregates the prediction models for different tags into a matrix, and casts tag ranking into a matrix recovery problem. It introduces the matrix trace norm to explicitly control the model complexity, so that a reliable prediction model can be learned for tag ranking even when the tag space is large and the number of training images is limited. Experiments on multiple well-known image data sets demonstrate the effectiveness of the proposed framework for tag ranking compared with the state-of-the-art approaches for image annotation and tag ranking. PMID:25622318

  12. Sub-diffraction-limited optical imaging with superlens and hyperlens

    NASA Astrophysics Data System (ADS)

    Lee, Hyesog

    Optical microscopy has been the most widely used imaging tool in various research disciplines for the last century. However, it has fundamental resolution limit called the Diffraction Limit, which prevents it from observing objects smaller than half of the wavelength. This is caused by the inability of lenses, which are located at far field of the objects, to detect high spatial frequency information encoded in evanescent waves which decay away in the near field. Along with modern technological advancements especially in the field of nanotechnology, numerous innovative ideas sprung up in the past several decades in efforts to break the diffraction barrier and achieve nano-scale optical imaging. The most popular method up to date uses near-field scanning scheme which tends to be very slow and impractical for real-time imaging. Other methods require rather complex imaging optics and multiple measurements of the same sample. So far, true far-field and real-time sub-diffraction-limited optical imaging method is yet to be developed. Here I report new imaging schemes, Superlensing (Near and Far-field superlens) and Hyperlensing, which are capable of not only imaging beyond the Diffraction Limit in resolution but making real-time imaging possible. The Superlens enhances evanescent waves through surface plasmon (SP) resonance. The Far-field Superlens (FSL) scatters them into the far-field and the detected information is then used to numerically reconstruct high resolution image. Hyperlens concept utilizes unusual electromagnetic properties of metamaterials to deliver high spatial frequency information directly into the far-field. It magnifies nano-scale objects just enough for optical microscope to image and no post-imaging process is needed. In this dissertation, detailed experiment designs including nano-fabrication of the superlens and the hyperlens structures were proposed and the first ever imaging results were presented. The resolving power beyond the Diffraction

  13. Principle and experimental results of ultra-wideband noise radar imaging of a cylindrical conducting object using diffraction tomography

    NASA Astrophysics Data System (ADS)

    Shin, Hee Jung; Asmuth, Mark A.; Narayanan, Ram M.; Rangaswamy, Muralidhar

    2015-05-01

    In this paper, the principle, simulation, and experiment results of tomographic imaging of a cylindrical conducting object using random noise waveforms are presented. Theoretical analysis of scattering and the image reconstruction technique are developed based on physical optics approximation and Fourier diffraction tomography, respectively. The bistatic radar system is designed to transmit band-limited ultra-wideband (UWB) random noise waveforms at a fixed position, and a linear scanner allows a single receiving antenna to move along a horizontal axis for backward scattering measurement in the frequency range from 3-5 GHz. The reconstructed tomographic image of the rotating cylindrical conducting object based on experimental results are seen to be in good agreement with the simulation results, which demonstrates the capability of UWB noise radar for complete two-dimensional tomographic image reconstruction of a cylindrical conducting object.

  14. Imaging Techniques for Relativistic Beams: Issues and Limitations

    SciTech Connect

    Lumpkin, Alex H.; Wendt, Manfred; /Fermilab

    2012-02-01

    Characterizations of transverse profiles for low-power beams in the accelerators of the proposed linear colliders (ILC and CLIC) using imaging techniques are being evaluated. Assessments of the issues and limitations for imaging relativistic beams with intercepting scintillator or optical transition radiation screens are presented based on low-energy tests at the Fermilab A0 photoinjector and are planned for the Advanced Superconducting Test Accelerator at Fermilab. We have described several of the issues and limitations one encounters with the imaging of relativistic electron beams. We have reported our initial tests at the A0PI facility and our plans to extend these studies to the GeV scale at the ASTA facility. We also have plans to test these concepts with 23-GeV beams at the FACET facility at SLAC in the coming year. It appears the future remains bright for imaging techniques in ILC-relevant parameter space.

  15. Correlation and image compression for limited-bandwidth CCD.

    SciTech Connect

    Thompson, Douglas G.

    2005-07-01

    As radars move to Unmanned Aerial Vehicles with limited-bandwidth data downlinks, the amount of data stored and transmitted with each image becomes more significant. This document gives the results of a study to determine the effect of lossy compression in the image magnitude and phase on Coherent Change Detection (CCD). We examine 44 lossy compression types, plus lossless zlib compression, and test each compression method with over 600 CCD image pairs. We also derive theoretical predictions for the correlation for most of these compression schemes, which compare favorably with the experimental results. We recommend image transmission formats for limited-bandwidth programs having various requirements for CCD, including programs which cannot allow performance degradation and those which have stricter bandwidth requirements at the expense of CCD performance.

  16. Infrared Imaging and Spectroscopy Beyond the Diffraction Limit

    NASA Astrophysics Data System (ADS)

    Centrone, Andrea

    2015-07-01

    Progress in nanotechnology is enabled by and dependent on the availability of measurement methods with spatial resolution commensurate with nanomaterials' length scales. Chemical imaging techniques, such as scattering scanning near-field optical microscopy (s-SNOM) and photothermal-induced resonance (PTIR), have provided scientists with means of extracting rich chemical and structural information with nanoscale resolution. This review presents some basics of infrared spectroscopy and microscopy, followed by detailed descriptions of s-SNOM and PTIR working principles. Nanoscale spectra are compared with far-field macroscale spectra, which are widely used for chemical identification. Selected examples illustrate either technical aspects of the measurements or applications in materials science. Central to this review is the ability to record nanoscale infrared spectra because, although chemical maps enable immediate visualization, the spectra provide information to interpret the images and characterize the sample. The growing breadth of nanomaterials and biological applications suggest rapid growth for this field.

  17. En bloc temporal bone resections in squamous cell carcinoma of the ear. Technique, principles, and limits.

    PubMed

    Mazzoni, Antonio; Zanoletti, Elisabetta; Marioni, Gino; Martini, Alessandro

    2016-05-01

    Conclusions En bloc resection should always be primarily considered in ear carcinoma, also in advanced tumors growing beyond the walls of the external auditory canal, because it achieves a full specimen for histopathological evaluation and allows a correlation between clinical, pathological features, and outcomes. Objective and methods Dismal outcome of surgical and radiotherapic therapies for advanced ear carcinoma required a critical discussion of the oncological principles of treatment. Our analysis involved preliminarily a detailed description of surgical technique including the contribution of modern skull base microsurgery. Results Evident limits in diagnostic protocols, surgical treatment and outcome evaluation modalities pointed to the need of a new approach towards an accurate definition of pre-operative tumor location, size, and behavior. En bloc resection achieved a specimen for a final pathological evaluation and an adjunctive piecemeal excision was necessary only whenever resection was not felt falling in safe, tumor-free tissue. Chemotherapy and radiotherapy should be considered in selected cases for adjuvant treatment. PMID:26824405

  18. Multi-limit unsymmetrical MLIBD image restoration algorithm

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Cheng, Yiping; Chen, Zai-wang; Bo, Chen

    2012-11-01

    A novel multi-limit unsymmetrical iterative blind deconvolution(MLIBD) algorithm was presented to enhance the performance of adaptive optics image restoration.The algorithm enhances the reliability of iterative blind deconvolution by introducing the bandwidth limit into the frequency domain of point spread(PSF),and adopts the PSF dynamic support region estimation to improve the convergence speed.The unsymmetrical factor is automatically computed to advance its adaptivity.Image deconvolution comparing experiments between Richardson-Lucy IBD and MLIBD were done,and the result indicates that the iteration number is reduced by 22.4% and the peak signal-to-noise ratio is improved by 10.18dB with MLIBD method. The performance of MLIBD algorithm is outstanding in the images restoration the FK5-857 adaptive optics and the double-star adaptive optics.

  19. Diffraction-limited 10 microns imaging with 3 meter telescopes

    NASA Technical Reports Server (NTRS)

    Bloemhof, E. E.; Townes, C. H.; Vanderwyck, A. H. B.

    1986-01-01

    An IR imaging system that achieves diffraction-limited spatial resolution (about 0.8 arcsec) at 10 microns on 3-meter ground-based telescopes. The system uses a linear array of sensitive HgCdTe photodiodes, scanned in the direction perpendicular to the array axis, to form two-dimensional images. Scans are completed rapidly enough to freeze atmospheric fluctuations. Individual detectors are small compared to the diameter of the Airy disk, and images are oversampled heavily in the scan direction. This method has a number of advantages for studying small fields with very high spatial resolution, and has been applied successfully to the problem of directly imaging faint circumstellar dust shells.

  20. First-Principles Atomic Force Microscopy Image Simulations with Density Embedding Theory.

    PubMed

    Sakai, Yuki; Lee, Alex J; Chelikowsky, James R

    2016-05-11

    We present an efficient first-principles method for simulating noncontact atomic force microscopy (nc-AFM) images using a "frozen density" embedding theory. Frozen density embedding theory enables one to efficiently compute the tip-sample interaction by considering a sample as a frozen external field. This method reduces the extensive computational load of first-principles AFM simulations by avoiding consideration of the entire tip-sample system and focusing on the tip alone. We demonstrate that our simulation with frozen density embedding theory accurately reproduces full density functional theory simulations of freestanding hydrocarbon molecules while the computational time is significantly reduced. Our method also captures the electronic effect of a Cu(111) substrate on the AFM image of pentacene and reproduces the experimental AFM image of Cu2N on a Cu(100) surface. This approach is applicable for theoretical imaging applications on large molecules, two-dimensional materials, and materials surfaces. PMID:27050710

  1. Quantifying Deep-Imaging Limits of the VLA

    NASA Astrophysics Data System (ADS)

    Mayeshiba, Julia; Mayeshiba, J.; Rau, U.; Owen, F. N.

    2014-01-01

    The confusion limit is important to understand when conducting surveys of faint radio sources. The source count distributions derived from these surveys are indicative of the large-scale structure and evolution of the universe. The VLA’s confusion limit is not well-defined and astronomers have frequently observed below its current estimated confusion limit. Our study seeks to refine and understand these estimated values and their differences. In our study, we used sources from the center one square degree of the S3-SEX simulated sky made by Wilman et al. As a first step, we verified that our simulation matched observed trends of the confusion limit. During this process we studied the dependence of the achieved confusion limit on cleaning depth and PSF shape. We also reproduced the different limits seen by Frazer Owen in 2008 and NVSS. With this check completed, we then roughly estimated the confusion limits for the VLA’s four configurations. Our preliminary results showed that at an observing frequency of 1.4GHz , there is a confusion limit of 10µJy for the D Configuration and 5µJy for the C Configuration. These estimates are a factor of two lower than the lowest confusion limits reached by observers. While it is encouraging that our estimated confusion limits follow observed trends, more analysis of our process is needed. We could not accurately estimate confusion limits for the A and B configurations due to an artifact dominated image in the A Configuration and an estimated confusion limit that was too close to the noise level in the B Configuration. For the second part of our study we tested CASA’s source-finding algorithm. We found that as currently implemented, it has significant difficulty finding fainter sources.

  2. Sub-diffraction-limit imaging using mode multiplexing

    NASA Astrophysics Data System (ADS)

    Wang, Nan; Miyazaki, Jun; He, Jinping; Seto, Keisuke; Kobayashi, Takayoshi

    2015-05-01

    Pixel-by-pixel processed fluorescence difference microscopy is experimentally demonstrated by multiplexing excitation laser beams with Gaussian and donut spot shapes and then demultiplexing the fluorescent signals using lock-in amplifiers. With this scheme, a fixed sample of fluorescent spheres and a slice of mouse brain tissue are imaged with resolutions that exceed the diffraction limit. Compared to previously reported subtraction imaging techniques, this pixel-by-pixel scan can be applied to improve the resolution of a moving sample without introducing subtraction errors. The synchronized signal detection feature makes this method extendible to various applications.

  3. Diffraction-limited lucky imaging with a 12" commercial telescope

    NASA Astrophysics Data System (ADS)

    Baptista, Brian J.

    2014-08-01

    Here we demonstrate a novel lucky imaging camera which is designed to produce diffraction-limited imaging using small telescopes similar to ones used by many academic institutions for outreach and/or student training. We present a design that uses a Meade 12" SCT paired with an Andor iXon fast readout EMCCD. The PSF of the telescope is matched to the pixel size of the EMCCD by adding a simple, custom-fabricated, intervening optical system. We demonstrate performance of the system by observing both astronomical and terrestrial targets. The astronomical application requires simpler data reconstruction techniques as compared to the terrestrial case. We compare different lucky imaging registration and reconstruction algorithms for use with this imager for both astronomical and terrestrial targets. We also demonstrate how this type of instrument would be useful for both undergraduate and graduate student training. As an instructional aide, the instrument can provide a hands-on approach for teaching instrument design, standard data reduction techniques, lucky imaging data processing, and high resolution imaging concepts.

  4. Architectural principles for the design of wide band image analysis systems

    SciTech Connect

    Bruning, U.; Giloi, W.K.; Liedtke, C.E.

    1983-01-01

    To match an image-analysis system appropriately to the multistage nature of image analysis, the system should have: (1) an overall system architecture made up of several dedicated SIMD coprocessors connected through a bottleneck-free, high-speed communication structure; (2) data-structure types in hardware; and (3) a conventional computer for executing operating-system functions and application programs. Coprocessors may exist specifically for local image processing, FFT, list processing, and vector processing in general. All functions must be transparent to the user. The architectural principles of such a system and the policies and mechanisms for its realization are exemplified. 4 references.

  5. Compressing Image Data While Limiting the Effects of Data Losses

    NASA Technical Reports Server (NTRS)

    Kiely, Aaron; Klimesh, Matthew

    2006-01-01

    ICER is computer software that can perform both lossless and lossy compression and decompression of gray-scale-image data using discrete wavelet transforms. Designed for primary use in transmitting scientific image data from distant spacecraft to Earth, ICER incorporates an error-containment scheme that limits the adverse effects of loss of data and is well suited to the data packets transmitted by deep-space probes. The error-containment scheme includes utilization of the algorithm described in "Partitioning a Gridded Rectangle Into Smaller Rectangles " (NPO-30479), NASA Tech Briefs, Vol. 28, No. 7 (July 2004), page 56. ICER has performed well in onboard compression of thousands of images transmitted from the Mars Exploration Rovers.

  6. Pitfalls and Limitations of Radionuclide Renal Imaging in Adults.

    PubMed

    Keramida, Georgia; James, Jacqueline M; Prescott, Mary C; Peters, Adrien Michael

    2015-09-01

    To understand pitfalls and limitations in adult renography, it is necessary to understand firstly the physiology of the kidney, especially the magnitude and control of renal blood flow, glomerular filtration rate and tubular fluid flow rate, and secondly the pharmacokinetics and renal handling of the three most often used tracers, Tc-99m-mercaptoacetyltriglycine (MAG3), Tc-99m-diethylene triamine pentaacetic acid (DTPA) and Tc-99m-dimercaptosuccinic acid (DMSA). The kidneys may be imaged dynamically with Tc-99m-MAG3 or Tc-99m-DTPA, with or without diuretic challenge, or by static imaging with Tc-99m-DMSA. Protocols are different according to whether the kidney is native or transplanted. Quantitative analysis of dynamic data includes measurement of renal vascularity (important for the transplanted kidney), absolute tracer clearance rates, differential renal function (DRF) and response to diuretic challenge. Static image reveals functional renal parenchymal damage, both focal and global, is useful in the clinical management of obstructive uropathy, renal stone disease and hypertension (under angiotensin converting enzyme inhibition), and is the preferred technique for determining DRF. Diagnosis based on morphological appearances is important in transplant management. Even though nuclear medicine is now in the era of hybrid imaging, renal imaging remains an important subspecialty in nuclear medicine and requires a sound basing in applied physiology, the classical supporting discipline of nuclear medicine. PMID:26278854

  7. High resolution transmission electron microscope Imaging and first-principles simulations of atomic-scale features in graphene membrane

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Bhandari, Sagar; Yi, Wei; Bell, David; Westervelt, Robert; Kaxiras, Efthimios

    2012-02-01

    Ultra-thin membranes such as graphene[1] are of great importance for basic science and technology applications. Graphene sets the ultimate limit of thinness, demonstrating that a free-standing single atomic layer not only exists but can be extremely stable and strong [2--4]. However, both theory [5, 6] and experiments [3, 7] suggest that the existence of graphene relies on intrinsic ripples that suppress the long-wavelength thermal fluctuations which otherwise spontaneously destroy long range order in a two dimensional system. Here we show direct imaging of the atomic features in graphene including the ripples resolved using monochromatic aberration-corrected transmission electron microscopy (TEM). We compare the images observed in TEM with simulated images based on an accurate first-principles total potential. We show that these atomic scale features can be mapped through accurate first-principles simulations into high resolution TEM contrast. [1] Geim, A. K. & Novoselov, K. S. Nat. Mater. 6, 183-191, (2007). [2] Novoselov, K. S.et al. Science 306, 666-669, (2004). [3] Meyer, J. C. et al. Nature 446, 60-63, (2007). [4] Lee, C., Wei, X. D., Kysar, J. W. & Hone, J. Science 321, 385-388, (2008). [5] Nelson, D. R. & Peliti, L. J Phys-Paris 48, 1085-1092, (1987). [6] Fasolino, A., Los, J. H. & Katsnelson, M. I. Nat. Mater. 6, 858-861, (2007). [7] Meyer, J. C. et al. Solid State Commun. 143, 101-109, (2007).

  8. Confidence Level and Sensitivity Limits in High Contrast Imaging

    SciTech Connect

    Marois, C

    2007-11-07

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

  9. Confidence Level and Sensitivity Limits in High Contrast Imaging

    SciTech Connect

    Marois, C; LaFreniere, D; Macintosh, B; Doyon, R

    2008-06-02

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

  10. Enhancement of positron emission tomography-computed tomography image quality using the principle of stochastic resonance

    PubMed Central

    Pandey, Anil Kumar; Sharma, Sanjay Kumar; Sharma, Punit; Singh, Harmandeep; Patel, Chetan; Sarkar, Kaushik; Kumar, Rakesh; Bal, Chandra Sekhar

    2014-01-01

    Purpose: Acquisition of higher counts improves visual perception of positron emission tomography-computed tomography (PET-CT) image. Larger radiopharmaceutical doses (implies more radiation dose) are administered to acquire this count in a short time period. However, diagnostic information does not increase after a certain threshold of counts. This study was conducted to develop a post processing method based on principle of “stochastic resonance” to improve visual perception of the PET-CT image having a required threshold counts. Materials and Methods: PET-CT images (JPEG file format) with low, medium, and high counts in the image were included in this study. The image was corrupted with the addition of Poisson noise. The amplitude of the Poisson noise was adjusted by dividing each pixel by a constant 1, 2, 4, 8, 16, and 32. The best amplitude of the noise that gave best images quality was selected based on high value of entropy of the output image, high value of structural similarity index and feature similarity index. Visual perception of the image was evaluated by two nuclear medicine physicians. Results: The variation in structural and feature similarity of the image was not appreciable visually, but statistically images deteriorated as the noise amplitude increases although maintaining structural (above 70%) and feature (above 80%) similarity of input images in all cases. We obtained the best image quality at noise amplitude “4” in which 88% structural and 95% feature similarity of the input images was retained. Conclusion: This method of stochastic resonance can be used to improve the visual perception of the PET-CT image. This can indirectly lead to reduction of radiation dose. PMID:25400362

  11. Iterative Image Reconstruction for Limited-Angle CT Using Optimized Initial Image

    PubMed Central

    Guo, Jingyu; Qi, Hongliang; Xu, Yuan; Chen, Zijia; Li, Shulong; Zhou, Linghong

    2016-01-01

    Limited-angle computed tomography (CT) has great impact in some clinical applications. Existing iterative reconstruction algorithms could not reconstruct high-quality images, leading to severe artifacts nearby edges. Optimal selection of initial image would influence the iterative reconstruction performance but has not been studied deeply yet. In this work, we proposed to generate optimized initial image followed by total variation (TV) based iterative reconstruction considering the feature of image symmetry. The simulated data and real data reconstruction results indicate that the proposed method effectively removes the artifacts nearby edges. PMID:27066107

  12. Radiological images on personal computers: introduction and fundamental principles of digital images.

    PubMed

    Gillespy, T; Rowberg, A H

    1993-05-01

    This series of articles will explore the issue related to displaying, manipulating, and analyzing radiological images on personal computers (PC). This first article discusses the digital image data file, standard PC graphic file formats, and various methods for importing radiological images into the PC. PMID:8334176

  13. Diffusion-weighted imaging in pediatric body MR imaging: principles, technique, and emerging applications.

    PubMed

    Chavhan, Govind B; Alsabban, Zehour; Babyn, Paul S

    2014-01-01

    Diffusion-weighted (DW) imaging is an emerging technique in body imaging that provides indirect information about the microenvironment of tissues and lesions and helps detect, characterize, and follow up abnormalities. Two main challenges in the application of DW imaging to body imaging are the decreased signal-to-noise ratio of body tissues compared with neuronal tissues due to their shorter T2 relaxation time, and image degradation related to physiologic motion (eg, respiratory motion). Use of smaller b values and newer motion compensation techniques allow the evaluation of anatomic structures with DW imaging. DW imaging can be performed as a breath-hold sequence or a free-breathing sequence with or without respiratory triggering. Depending on the mobility of water molecules in their microenvironment, different normal tissues have different signals at DW imaging. Some normal tissues (eg, lymph nodes, spleen, ovarian and testicular parenchyma) are diffusion restricted, whereas others (eg, gallbladder, corpora cavernosa, endometrium, cartilage) show T2 shine-through. Epiphyses that contain fatty marrow and bone cortex appear dark on both DW images and apparent diffusion coefficient maps. Current and emerging applications of DW imaging in pediatric body imaging include tumor detection and characterization, assessment of therapy response and monitoring of tumors, noninvasive detection and grading of liver fibrosis and cirrhosis, detection of abscesses, and evaluation of inflammatory bowel disease. PMID:24819803

  14. Quantitative Phase Imaging Techniques for the Study of Cell Pathophysiology: From Principles to Applications

    PubMed Central

    Lee, KyeoReh; Kim, Kyoohyun; Jung, Jaehwang; Heo, JiHan; Cho, Sangyeon; Lee, Sangyun; Chang, Gyuyoung; Jo, YoungJu; Park, Hyunjoo; Park, YongKeun

    2013-01-01

    A cellular-level study of the pathophysiology is crucial for understanding the mechanisms behind human diseases. Recent advances in quantitative phase imaging (QPI) techniques show promises for the cellular-level understanding of the pathophysiology of diseases. To provide important insight on how the QPI techniques potentially improve the study of cell pathophysiology, here we present the principles of QPI and highlight some of the recent applications of QPI ranging from cell homeostasis to infectious diseases and cancer. PMID:23539026

  15. Confidence Level and Sensitivity Limits in High-Contrast Imaging

    NASA Astrophysics Data System (ADS)

    Marois, Christian; Lafrenière, David; Macintosh, Bruce; Doyon, René

    2008-01-01

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground- and space-based telescopes. Previous theoretical analyses have shown that the time intensity variations of a single speckle follow a modified Rician. It is first demonstrated here that for a circular pupil, this temporal intensity distribution also represents the speckle spatial intensity distribution at a fixed separation from the point-spread function center; this fact is demonstrated using numerical simulations for coronagraphic and noncoronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level (CL). In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding CL as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckle noise, a detection threshold up to 3 times higher is required to obtain a CL equivalent to that at 5 σ for Gaussian noise. The technique is then tested on data acquired by simultaneous spectral differential imaging with TRIDENT and by angular differential imaging with NIRI. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. Finally, a power law is derived to predict the 1 - 3 × 10-7 CL detection threshold when averaging a partially correlated non-Gaussian noise. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of

  16. Principles and Applications of Imaging Radar, Manual of Remote Sensing, 3rd Edition, Volume 2

    NASA Astrophysics Data System (ADS)

    Moran, M. Susan

    Aerial photographs and digital images from orbiting optical scanners are a daily source of information for the general public through newspapers, television, magazines, and posters. Such images are just as prevalent in scientific journal literature. In the last 6 months, more than half of the weekly issues of Eos published an image acquired by a remote digital sensor. As a result, most geoscientists are familiar with the characteristics and even the acronyms of the current satellites and their optical sensors, common detector filters, and image presentation. In many cases, this familiarity has bred contempt. This is so because the limitations of optical sensors (imaging in the visible and infrared portions of the electromagnetic spectrum) can be quite formidable. Images of the surface cannot be acquired through clouds, and image quality is impaired with low-light conditions (such as at polar regions), atmospheric scattering and absorption, and variations in sun/sensor/surface geometry.

  17. Laser speckle contrast imaging: theoretical and practical limitations.

    PubMed

    Briers, David; Duncan, Donald D; Hirst, Evan; Kirkpatrick, Sean J; Larsson, Marcus; Steenbergen, Wiendelt; Stromberg, Tomas; Thompson, Oliver B

    2013-06-01

    When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide information about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale-the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle contrast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimensional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its limitations and problems are investigated. PMID:23807512

  18. Recovery of microfields in fiber-reinforced composite materials: Principles and limitations

    NASA Astrophysics Data System (ADS)

    Ritchey, Andrew J.

    A detailed investigation of the limitations and errors induced by modeling a composite layer composed of straight carbon fibers embedded in an epoxy matrix as an homogenous layer with Cauchy effective moduli is performed. Specifically, the material system studied has IM7 carbon fibers arranged in a square array and bonded together with 8552 epoxy resin (IM7/8552). The finite element method is used to study the effect of free surfaces on the local elastic fields in 0°, 45° and 90° laminae, in which as many as 256 individual fibers are modeled. Through these analyses, it is shown that a micro-boundary layer, analogous to the macro-boundary layer observed in composite laminates, is developed at the microlevel. Additionally, [0/90]s and [90/0]s laminates are studied to investigate the joint action of the macro- and micro-boundary layers. Unless otherwise noted, fiber volume fractions of Vƒ=0.20 and Vƒ=0.65 are selected and the domains are subjected to uniform axial extension. Although this study is done for a highly idealized geometry (i.e. with a single material system and under a simple loading condition) the principles of periodicity, symmetry and antisymmetry used to efficiently perform a direct numerical simulation with a large number of fiber inclusions is general, and can be applied to more complicated geometries and boundary conditions. The purpose of the current work is to be the first step in a building block approach to understanding the interaction of multiple scales in fiber-reinforced composites through direct numerical simulations. The main part of the current manuscript focuses on the characterization of a micro-boundary layer that develops in fiber reinforced composite layers. This phenomena results from the changing constraints on the constituent phases as a result of discontinuities, such as free surfaces or ply interfaces. The effect is most pronounced in laminae that have a fiber termination intersecting a free surface, and appears to be

  19. Observer detection limits for a dedicated SPECT breast imaging system

    NASA Astrophysics Data System (ADS)

    Cutler, S. J.; Perez, K. L.; Barnhart, H. X.; Tornai, M. P.

    2010-04-01

    An observer-based contrast-detail study is performed in an effort to evaluate the limits of object detectability using a dedicated CZT-based breast SPECT imaging system under various imaging conditions. A custom geometric contrast-resolution phantom was developed that can be used for both positive ('hot') and negative contrasts ('cold'). The 3 cm long fillable tubes are arranged in six sectors having equal inner diameters ranging from 1 mm to 6 mm with plastic wall thicknesses of <0.25 mm, on a pitch of twice their inner diameters. Scans of the activity filled tubes using simple circular trajectories are obtained in a 215 mL uniform water filled cylinder, varying the rod:background concentration ratios from 10:1 to 1:10 simulating a large range of biological uptake ratios. The rod phantom is then placed inside a non-uniformly shaped 500 mL breast phantom and scans are again acquired using both simple and complex 3D trajectories for similarly varying contrasts. Summed slice and contiguous multi-slice images are evaluated by five independent readers, identifying the smallest distinguishable rod for each concentration and experimental setup. Linear and quadratic regression is used to compare the resulting contrast-detail curves. Results indicate that in a moderately low-noise 500 mL background, using the SPECT camera having 2.5 mm intrinsic pixels, the mean detectable rod was ~3.4 mm at a 10:1 ratio, degrading to ~5.2 mm with the 2.5:1 concentration ratio. The smallest object detail was observed using a 45° tilted trajectory acquisition. The complex 3D projected sine wave acquisition, however, had the most consistent combined intra- and inter-observer results, making it potentially the best imaging approach for consistent results.

  20. Principles and applications of hyperspectral imaging in quality evaluation of agro-food products: a review.

    PubMed

    Elmasry, Gamal; Kamruzzaman, Mohammed; Sun, Da-Wen; Allen, Paul

    2012-01-01

    The requirements of reliability, expeditiousness, accuracy, consistency, and simplicity for quality assessment of food products encouraged the development of non-destructive technologies to meet the demands of consumers to obtain superior food qualities. Hyperspectral imaging is one of the most promising techniques currently investigated for quality evaluation purposes in numerous sorts of applications. The main advantage of the hyperspectral imaging system is its aptitude to incorporate both spectroscopy and imaging techniques not only to make a direct assessment of different components simultaneously but also to locate the spatial distribution of such components in the tested products. Associated with multivariate analysis protocols, hyperspectral imaging shows a convinced attitude to be dominated in food authentication and analysis in future. The marvellous potential of the hyperspectral imaging technique as a non-destructive tool has driven the development of more sophisticated hyperspectral imaging systems in food applications. The aim of this review is to give detailed outlines about the theory and principles of hyperspectral imaging and to focus primarily on its applications in the field of quality evaluation of agro-food products as well as its future applicability in modern food industries and research. PMID:22823348

  1. Dual-Energy CT: Basic Principles, Technical Approaches, and Applications in Musculoskeletal Imaging (Part 1).

    PubMed

    Omoumi, Patrick; Becce, Fabio; Racine, Damien; Ott, Julien G; Andreisek, Gustav; Verdun, Francis R

    2015-12-01

    In recent years, technological advances have allowed manufacturers to implement dual-energy computed tomography (DECT) on clinical scanners. With its unique ability to differentiate basis materials by their atomic number, DECT has opened new perspectives in imaging. DECT has been used successfully in musculoskeletal imaging with applications ranging from detection, characterization, and quantification of crystal and iron deposits; to simulation of noncalcium (improving the visualization of bone marrow lesions) or noniodine images. Furthermore, the data acquired with DECT can be postprocessed to generate monoenergetic images of varying kiloelectron volts, providing new methods for image contrast optimization as well as metal artifact reduction. The first part of this article reviews the basic principles and technical aspects of DECT including radiation dose considerations. The second part focuses on applications of DECT to musculoskeletal imaging including gout and other crystal-induced arthropathies, virtual noncalcium images for the study of bone marrow lesions, the study of collagenous structures, applications in computed tomography arthrography, as well as the detection of hemosiderin and metal particles. PMID:26696081

  2. Dual-Energy CT: Basic Principles, Technical Approaches, and Applications in Musculoskeletal Imaging (Part 2).

    PubMed

    Omoumi, Patrick; Verdun, Francis R; Guggenberger, Roman; Andreisek, Gustav; Becce, Fabio

    2015-12-01

    In recent years, technological advances have allowed manufacturers to implement dual-energy computed tomography (DECT) on clinical scanners. With its unique ability to differentiate basis materials by their atomic number, DECT has opened new perspectives in imaging. DECT has been successfully used in musculoskeletal imaging with applications ranging from detection, characterization, and quantification of crystal and iron deposits, to simulation of noncalcium (improving the visualization of bone marrow lesions) or noniodine images. Furthermore, the data acquired with DECT can be postprocessed to generate monoenergetic images of varying kiloelectron volts, providing new methods for image contrast optimization as well as metal artifact reduction. The first part of this article reviews the basic principles and technical aspects of DECT including radiation dose considerations. The second part focuses on applications of DECT to musculoskeletal imaging including gout and other crystal-induced arthropathies, virtual noncalcium images for the study of bone marrow lesions, the study of collagenous structures, applications in computed tomography arthrography, as well as the detection of hemosiderin and metal particles. PMID:26696082

  3. Systematic, spatial imaging of large multimolecular assemblies and the emerging principles of supramolecular order in biological systems

    PubMed Central

    Schubert, Walter

    2013-01-01

    Understanding biological systems at the level of their relational (emergent) molecular properties in functional protein networks relies on imaging methods, able to spatially resolve a tissue or a cell as a giant, non-random, topologically defined collection of interacting supermolecules executing myriads of subcellular mechanisms. Here, the development and findings of parameter-unlimited functional super-resolution microscopy are described—a technology based on the fluorescence imaging cycler (IC) principle capable of co-mapping thousands of distinct biomolecular assemblies at high spatial resolution and differentiation (<40 nm distances). It is shown that the subcellular and transcellular features of such supermolecules can be described at the compositional and constitutional levels; that the spatial connection, relational stoichiometry, and topology of supermolecules generate hitherto unrecognized functional self-segmentation of biological tissues; that hierarchical features, common to thousands of simultaneously imaged supermolecules, can be identified; and how the resulting supramolecular order relates to spatial coding of cellular functionalities in biological systems. A large body of observations with IC molecular systems microscopy collected over 20 years have disclosed principles governed by a law of supramolecular segregation of cellular functionalities. This pervades phenomena, such as exceptional orderliness, functional selectivity, combinatorial and spatial periodicity, and hierarchical organization of large molecular systems, across all species investigated so far. This insight is based on the high degree of specificity, selectivity, and sensitivity of molecular recognition processes for fluorescence imaging beyond the spectral resolution limit, using probe libraries controlled by ICs. © 2013 The Authors. Journal of Molecular Recognition published by John Wiley & Sons, Ltd. PMID:24375580

  4. Design Principles of Nanoparticles as Contrast Agents for Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Shan, Liang; Gu, Xinbin; Wang, Paul

    2013-09-01

    Molecular imaging is an emerging field that introduces molecular agents into traditional imaging techniques, enabling visualization, characterization and measurement of biological processes at the molecular and cellular levels in humans and other living systems. The promise of molecular imaging lies in its potential for selective potency by targeting biomarkers or molecular targets and the imaging agents serve as reporters for the selectivity of targeting. Development of an efficient molecular imaging agent depends on well-controlled high-quality experiment design involving target selection, agent synthesis, in vitro characterization, and in vivo animal characterization before it is applied in humans. According to the analysis from the Molecular Imaging and Contrast Agent Database (MICAD, ), more than 6000 molecular imaging agents with sufficient preclinical evaluation have been reported to date in the literature and this number increases by 250-300 novel agents each year. The majority of these agents are radionuclides, which are developed for positron emission tomography (PET) and single photon emission computed tomography (SPECT). Contrast agents for magnetic resonance imaging (MRI) account for only a small part. This is largely due to the fact that MRI is currently not a fully quantitative imaging technique and is less sensitive than PET and SPECT. However, because of the superior ability to simultaneously extract molecular and anatomic information, molecular MRI is attracting significant interest and various targeted nanoparticle contrast agents have been synthesized for MRI. The first and one of the most critical steps in developing a targeted nanoparticle contrast agent is target selection, which plays the central role and forms the basis for success of molecular imaging. This chapter discusses the design principles of targeted contrast agents in the emerging frontiers of molecular MRI.

  5. UCXp camera imaging principle and key technologies of data post-processing

    NASA Astrophysics Data System (ADS)

    Yuan, Fangyan; Li, Guoqing; Zuo, Zhengli; Liu, Jianmin; Wu, Liang; Yu, Xiaoping; Zhao, Haitao

    2014-03-01

    The large format digital aerial camera product UCXp was introduced into the Chinese market in 2008, the image consists of 17310 columns and 11310 rows with a pixel size of 6 mm. The UCXp camera has many advantages compared with the same generation camera, with multiple lenses exposed almost at the same time and no oblique lens. The camera has a complex imaging process whose principle will be detailed in this paper. On the other hand, the UCXp image post-processing method, including data pre-processing and orthophoto production, will be emphasized in this article. Based on the data of new Beichuan County, this paper will describe the data processing and effects.

  6. Direct method of three-dimensional imaging using the multiple-wavelength range-gated active imaging principle.

    PubMed

    Matwyschuk, Alexis

    2016-05-10

    The tomography executed with mono-wavelength active imaging systems uses the recording of several images to restore a three-dimensional (3D) scene. Thus, in order to show the depth in the scene, a different color is attributed to each recorded image. Therefore, the 3D restoration depends on the video frame rate of the camera. By using a multiple-wavelength range-gated active imaging system, it is possible to restore the 3D scene directly in a single image at the moment of recording with a video camera. Each emitted light pulse with a different wavelength corresponds to a visualized zone at a different distance in the scene. The camera shutter opens just once during the emission of light pulses with the different wavelengths. Thus, the restoration can be executed in real time with regard to the video frame rate of the camera. From an analytical model and from a graphical approach, we demonstrated the feasibility of this new method of 3D restoration. The non-overlapping conditions between two consecutive visualized zones are analyzed. The experimental test results confirm these different conditions and validate the theoretical principle to directly restore the 3D scene in a color image with a multiple-wavelength laser source, an RGB filter, and a triggerable intensified camera. PMID:27168293

  7. New Limits on the Strong Equivalence Principle from Two Long-period Circular-orbit Binary Pulsars

    NASA Astrophysics Data System (ADS)

    Lorimer, D. R.; Freire, P. C. C.

    2005-07-01

    Following a brief review of the principles of the strong equivalence principle (SEP) and tests for its violation in the strong and weak gravitational field regimes, we present preliminary results of new tests using two long-period binary pulsars: J0407+1607 and J2016+1947. PSR J0407+1607 is in a 669-day orbit around a ≳ 0.2 M⊙ companion, while J2016+1947 is in a 635-day orbit around a ≳ 0.3 M⊙ companion. The small eccentricities of both orbits (e ˜ 10-3) mean that these systems reduce previous limits on SEP violation by more than a factor of 4.

  8. Thermal infrared imaging in psychophysiology: Potentialities and limits

    PubMed Central

    Ioannou, Stephanos; Gallese, Vittorio; Merla, Arcangelo

    2014-01-01

    Functional infrared thermal imaging (fITI) is considered an upcoming, promising methodology in the emotional arena. Driven by sympathetic nerves, observations of affective nature derive from muscular activity subcutaneous blood flow as well as perspiration patterns in specific body parts. A review of 23 experimental procedures that employed fITI for investigations of affective nature is provided, along with the adopted experimental protocol and the thermal changes that took place on selected regions of interest in human and nonhuman subjects. Discussion is provided regarding the selection of an appropriate baseline, the autonomic nature of the thermal print, the experimental setup, methodological issues, limitations, and considerations, as well as future directions. PMID:24961292

  9. Diffraction-limited step-zoom telescope by image restoration.

    PubMed

    Araiza-Durán, José A; Luna, Esteban; Cornejo-Rodríguez, Alejandro; Sohn, Erika

    2015-11-10

    The design of a step-zoom telescope and its ability to achieve a diffraction-limited performance is explored. The basic idea is to include digital postprocessing to compensate for changes in the modulation transfer function of the system, assuming the knowledge of the range to the object. The instrument is conformed of a two-mirror telescope, two lenses, and a detector. High-quality images and a zoom telescope that ranges from 22 to 61 f-number is achieved by moving the primary mirror and two lenses. The preliminary calculations for the design process and a simulation that shows the performance of the step-zoom telescope are described. PMID:26560774

  10. T1ρ magnetic resonance: basic physics principles and applications in knee and intervertebral disc imaging

    PubMed Central

    Zhang, Qinwei; Li, Xiaojuan; Chen, Weitian; Ahuja, Anil; Yuan, Jing

    2015-01-01

    T1ρ relaxation time provides a new contrast mechanism that differs from T1- and T2-weighted contrast, and is useful to study low-frequency motional processes and chemical exchange in biological tissues. T1ρ imaging can be performed in the forms of T1ρ-weighted image, T1ρ mapping and T1ρ dispersion. T1ρ imaging, particularly at low spin-lock frequency, is sensitive to B0 and B1 inhomogeneity. Various composite spin-lock pulses have been proposed to alleviate the influence of field inhomogeneity so as to reduce the banding-like spin-lock artifacts. T1ρ imaging could be specific absorption rate (SAR) intensive and time consuming. Efforts to address these issues and speed-up data acquisition are being explored to facilitate wider clinical applications. This paper reviews the T1ρ imaging’s basic physic principles, as well as its application for cartilage imaging and intervertebral disc imaging. Compared to more established T2 relaxation time, it has been shown that T1ρ provides more sensitive detection of proteoglycan (PG) loss at early stages of cartilage degeneration. T1ρ has also been shown to provide more sensitive evaluation of annulus fibrosis (AF) degeneration of the discs. PMID:26807369

  11. Diffraction-limited imaging on the 200-inch telescope

    NASA Astrophysics Data System (ADS)

    Nakajima, Tadashi

    The technique of non-redundant masking at the Palomar 200-inch telescope and radio VLBI imaging software was used to make optical aperture synthesis maps of two binary stars, Beta Corona Borealis and Sigma Herculis. The dynamic range of the map of Beta CrB, a binary star with a separation of 230 milliarcseconds is 50:1. For Sigma Her, a separation of 70 milliarcseconds was found and the dynamic range of the image is 30:1. These demonstrate the potential of the non-redundant masking technique for diffraction limited imaging of astronomical objects with high dynamic range. It was found that the optimal integration time for measuring the closure phase is longer than that for measuring the fringe amplitude. There is not a close relationship between amplitude errors and phase errors, as is found in radio interferometry. Amplitude self calibration is less effective at optical wavelengths than at radio wavelengths. Primary beam sensitivity correction made in radio aperture is not necessary in optical aperture synthesis. Effects of atmospheric disturbances on optical aperture synthesis were studied by Monte Carlo simulations based on the Kolmogorov theory of refractive-index fluctuations. For the non-redundant masking technique with rc-sized apertures, the simulated fringe amplitude gives an upper bound of the observed fringe amplitude. Monte Carlo simulations are also made to study the sensitivity and resolution of the bispectral analysis of speckle interferometry. The bispectral modulation transfer function and its signal-to-noise ratio at high light levels is presented. The signal-to-noise ratio of the bispectrum at arbitrary light levels is derived in the mid-spatial-frequency range.

  12. Limitations of visual assessment of redistribution in thallium images

    SciTech Connect

    DiCola, J.; Moore, M.; Shearer, D.; O'Reilly, G.; Most, A.S.; Gewirtz, H.

    1984-10-01

    Potential limitations of visual assessment of redistribution in thallium (TI) images were studied and results were compared with computer assessment of redistribution. A four-section phantom filled with TI was imaged (300K counts, 128 X 128 matrix) with appropriate background activity and scatter material. Activity in a ''defect'' section (DS) was varied from 20% to 100% of reference sections (RS). After interpolative background correction, pseudo ''initial'' and ''late'' image pairs (N . 35) were photographed on polaroid film and read by three ''blinded'' observers using an 0-2, 1/2 step, scale (0 . absent and 2 . normal activity). Scan defects were detected by all readers when DS activity was less than or equal to 59% of RS activity. No reader detected a defect when DS activity was greater than or equal to 67% of RS activity. All ''initial'' defects were detected by computer analysis. Visual assessment of ''initial'' DS:RS activity ratio did not correlate well with DS:RS activity ratio of the phantom. In contrast, computer assessment of ''initial'' DS:RS activity ratio correlated well with phantom DS:RS activity ratio (r . 0.96, p less than .0001). Although 22 of 27 scan pairs with partial (N . 26) or full (N . 1) redistribution were correctly identified as showing redistribution by at least two of three observers, the extent of redistribution was not estimated well by visual analysis. Thus, visual assessment of absolute change (''initial''-to-''late'') in DS:RS activity ratio showed considerable scatter in relations to actual changes in DS:RS activity ratio of the phantom.

  13. Distance-limited dispersal promotes coexistence at habitat boundaries: reconsidering the competitive exclusion principle.

    PubMed

    Débarre, Florence; Lenormand, Thomas

    2011-03-01

    Understanding the conditions for the stable coexistence of different alleles or species is a central topic in theoretical evolution and ecology. Different causes for stable polymorphism or species coexistence have already been identified but they can be grouped into a limited number of general processes. This article is devoted to the presentation and illustration of a new process, which we call 'habitat boundary polymorphism', and which relies on two key ingredients: habitat heterogeneity and distance-limited dispersal. Under direct competition and with fixed population densities, we show that this process allows for the equilibrium coexistence of more than n types in a n-habitat environment. Distance-limited dispersal indeed creates local maladaptation at habitat edges, which leaves room for the invasion of more generalist alleles or species. This mechanism provides a generic yet neglected process for the maintenance of polymorphism or species coexistence. PMID:21265974

  14. Design principles for single standing nanowire solar cells: going beyond the planar efficiency limits

    PubMed Central

    Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

    2014-01-01

    Semiconductor nanowires (NWs) have long been used in photovoltaic applications but restricted to approaching the fundamental efficiency limits of the planar devices with less material. However, recent researches on standing NWs have started to reveal their potential of surpassing these limits when their unique optical property is utilized in novel manners. Here, we present a theoretical guideline for maximizing the conversion efficiency of a single standing NW cell based on a detailed study of its optical absorption mechanism. Under normal incidence, a standing NW behaves as a dielectric resonator antenna, and its optical cross-section shows its maximum when the lowest hybrid mode (HE11δ) is excited along with the presence of a back-reflector. The promotion of the cell efficiency beyond the planar limits is attributed to two effects: the built-in concentration caused by the enlarged optical cross-section, and the shifting of the absorption front resulted from the excited mode profile. By choosing an optimal NW radius to support the HE11δ mode within the main absorption spectrum, we demonstrate a relative conversion-efficiency enhancement of 33% above the planar cell limit on the exemplary a-Si solar cells. This work has provided a new basis for designing and analyzing standing NW based solar cells. PMID:24810591

  15. Minimum current principle and variational method in theory of space charge limited flow

    SciTech Connect

    Rokhlenko, A.

    2015-10-21

    In spirit of the principle of least action, which means that when a perturbation is applied to a physical system, its reaction is such that it modifies its state to “agree” with the perturbation by “minimal” change of its initial state. In particular, the electron field emission should produce the minimum current consistent with boundary conditions. It can be found theoretically by solving corresponding equations using different techniques. We apply here the variational method for the current calculation, which can be quite effective even when involving a short set of trial functions. The approach to a better result can be monitored by the total current that should decrease when we on the right track. Here, we present only an illustration for simple geometries of devices with the electron flow. The development of these methods can be useful when the emitter and/or anode shapes make difficult the use of standard approaches. Though direct numerical calculations including particle-in-cell technique are very effective, but theoretical calculations can provide an important insight for understanding general features of flow formation and even sometimes be realized by simpler routines.

  16. Rapid methods for the detection of foodborne bacterial pathogens: principles, applications, advantages and limitations

    PubMed Central

    Law, Jodi Woan-Fei; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Lee, Learn-Han

    2015-01-01

    The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Foodborne pathogens can be found in various foods and it is important to detect foodborne pathogens to provide safe food supply and to prevent foodborne diseases. The conventional methods used to detect foodborne pathogen are time consuming and laborious. Hence, a variety of methods have been developed for rapid detection of foodborne pathogens as it is required in many food analyses. Rapid detection methods can be categorized into nucleic acid-based, biosensor-based and immunological-based methods. This review emphasizes on the principles and application of recent rapid methods for the detection of foodborne bacterial pathogens. Detection methods included are simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray which classified as nucleic acid-based methods; optical, electrochemical and mass-based biosensors which classified as biosensor-based methods; enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay which classified as immunological-based methods. In general, rapid detection methods are generally time-efficient, sensitive, specific and labor-saving. The developments of rapid detection methods are vital in prevention and treatment of foodborne diseases. PMID:25628612

  17. Rapid methods for the detection of foodborne bacterial pathogens: principles, applications, advantages and limitations.

    PubMed

    Law, Jodi Woan-Fei; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Lee, Learn-Han

    2014-01-01

    The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Foodborne pathogens can be found in various foods and it is important to detect foodborne pathogens to provide safe food supply and to prevent foodborne diseases. The conventional methods used to detect foodborne pathogen are time consuming and laborious. Hence, a variety of methods have been developed for rapid detection of foodborne pathogens as it is required in many food analyses. Rapid detection methods can be categorized into nucleic acid-based, biosensor-based and immunological-based methods. This review emphasizes on the principles and application of recent rapid methods for the detection of foodborne bacterial pathogens. Detection methods included are simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray which classified as nucleic acid-based methods; optical, electrochemical and mass-based biosensors which classified as biosensor-based methods; enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay which classified as immunological-based methods. In general, rapid detection methods are generally time-efficient, sensitive, specific and labor-saving. The developments of rapid detection methods are vital in prevention and treatment of foodborne diseases. PMID:25628612

  18. Image reconstruction from limited angle projections collected by multisource interior x-ray imaging systems

    NASA Astrophysics Data System (ADS)

    Liu, Baodong; Wang, Ge; Ritman, Erik L.; Cao, Guohua; Lu, Jianping; Zhou, Otto; Zeng, Li; Yu, Hengyong

    2011-10-01

    A multisource x-ray interior imaging system with limited angle scanning is investigated to study the possibility of building an ultrafast micro-CT for dynamic small animal imaging, and two methods are employed to perform interior reconstruction from a limited number of projections collected by the multisource interior x-ray system. The first is total variation minimization with the steepest descent search (TVM-SD) and the second is total difference minimization with soft-threshold filtering (TDM-STF). Comprehensive numerical simulations and animal studies are performed to validate the associated reconstructed methods and demonstrate the feasibility and application of the proposed system configuration. The image reconstruction results show that both of the two reconstruction methods can significantly improve the image quality and the TDM-SFT is slightly superior to the TVM-SD. Finally, quantitative image analysis shows that it is possible to make an ultrafast micro-CT using a multisource interior x-ray system scheme combined with the state-of-the-art interior tomography.

  19. Lubrication with sputtered MoS2 films: Principles, operation, limitations

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1991-01-01

    The present practices, limitations, and understanding of thin sputtered MoS2 films are reviewed. Sputtered MoS2 films can exhibit remarkable tribological properties such as ultralow friction coefficients (0.01) and enhanced wear lives (millions of cycles) when used in vacuum or dry air. To achieve these favorable tribological characteristics, the sputtering conditions during deposition must be optimized for adequate film adherence and appropriate structure (morphology) and composition.

  20. Compact wavelength splitter based on self-imaging principles in Bragg reflection waveguides.

    PubMed

    Chen, Bing; Huang, Lin; Li, Yongdong; Liu, Chunliang; Liu, Guizhong

    2012-10-10

    The self-imaging phenomena in multimode Bragg reflection waveguides (BRWs) have been predicted and investigated by using the plane-wave expansion method and the finite-difference time-domain method. A compact wavelength splitter based on self-imaging principles in BRWs is presented, and its transmission characteristics are investigated by using the finite-difference time-domain method. Calculated results indicate that, for the wavelength splitter without any waveguide bend optimizations, two optical waves with different wavelengths can be spatially separated, and corresponding transmittances are 95.6% and 90.1%, respectively. The simple and compact wavelength splitter is expected to be applied to highly dense photonic integrated circuits. PMID:23052094

  1. Principles and applications of imaging radar. Manual of remote sensing: Third edition, Volume 2

    SciTech Connect

    Henderson, F.M.; Lewis, A.J.

    1998-12-31

    This second volume in the Third Edition of the Manual of Remote Sensing offers a current and comprehensive survey of the theory, methods, and applications of imaging radar for geoscientists, engineers and application scientists interested in the advantages of radar remote sensing. Produced under the auspices of the American Society for Photogrammetry and Remote Sensing, it brings together contributions from experts around the world to discuss the basic principles of imaging radars and trace the research activity--past, present, and future--across the many sciences where radar remote sensing may be applied. This book offers an invaluable snapshot of radar remote sensing technology, including radargrammetry, radar polarimetry and interferometry and its uses. It combines technical and procedural coverage of systems, data interpretation, and other fundamentals with generous coverage of practical applications in agriculture; forestry; soil moisture monitoring; geology; geomorphology and hydrology; oceanography; land use, land cover mapping and archeology.

  2. Limits on violations of Lorentz symmetry and the Einstein equivalence principle using radio-frequency spectroscopy of atomic dysprosium.

    PubMed

    Hohensee, M A; Leefer, N; Budker, D; Harabati, C; Dzuba, V A; Flambaum, V V

    2013-08-01

    We report a joint test of local Lorentz invariance and the Einstein equivalence principle for electrons, using long-term measurements of the transition frequency between two nearly degenerate states of atomic dysprosium. We present many-body calculations which demonstrate that the energy splitting of these states is particularly sensitive to violations of both special and general relativity. We limit Lorentz violation for electrons at the level of 10(-17), matching or improving the best laboratory and astrophysical limits by up to a factor of 10, and improve bounds on gravitational redshift anomalies for electrons by 2 orders of magnitude, to 10(-8). With some enhancements, our experiment may be sensitive to Lorentz violation at the level of 9 × 10(-20). PMID:23952369

  3. The Global Landscape of Occupational Exposure Limits—Implementation of Harmonization Principles to Guide Limit Selection

    PubMed Central

    Deveau, M.; Chen, C-P; Johanson, G.; Krewski, D.; Maier, A.; Niven, K. J.; Ripple, S.; Schulte, P. A.; Silk, J.; Urbanus, J. H.; Zalk, D. M.; Niemeier, R. W.

    2015-01-01

    Occupational exposure limits (OELs) serve as health-based benchmarks against which measured or estimated workplace exposures can be compared. In the years since the introduction of OELs to public health practice, both developed and developing countries have established processes for deriving, setting, and using OELs to protect workers exposed to hazardous chemicals. These processes vary widely, however, and have thus resulted in a confusing international landscape for identifying and applying such limits in workplaces. The occupational hygienist will encounter significant overlap in coverage among organizations for many chemicals, while other important chemicals have OELs developed by few, if any, organizations. Where multiple organizations have published an OEL, the derived value often varies considerably—reflecting differences in both risk policy and risk assessment methodology as well as access to available pertinent data. This article explores the underlying reasons for variability in OELs, and recommends the harmonization of risk-based methods used by OEL-deriving organizations. A framework is also proposed for the identification and systematic evaluation of OEL resources, which occupational hygienists can use to support risk characterization and risk management decisions in situations where multiple potentially relevant OELs exist. PMID:26099071

  4. Methods to Assess Bioavailability of Hydrophobic Organic Contaminants: Principles, Operations, and Limitations

    PubMed Central

    Cui, Xinyi; Mayer, Philipp; Gan, Jay

    2013-01-01

    Many important environmental contaminants are hydrophobic organic contaminants (HOCs), which include PCBs, PAHs, PBDEs, DDT and other chlorinated insecticides, among others. Owing to their strong hydrophobicity, HOCs have their final destination in soil or sediment, where their ecotoxicological effects are closely regulated by sorption and thus bioavailability. The last two decades has seen a dramatic increase in research efforts in developing and applying partitioning based methods and biomimetic extractions for measuring HOC bioavailability. However, the many variations of both analytical methods and associated measurement endpoints are often a source of confusion for users. In this review, we distinguish the most commonly used analytical approaches based on their measurement objectives, and illustrate their practical operational steps, strengths and limitations using simple flowcharts. This review may serve as guidance for new users on the selection and use of established methods, and a reference for experienced investigators to identify potential topics for further research. PMID:23064200

  5. Al-Air Batteries: Fundamental Thermodynamic Limitations from First Principles Theory

    NASA Astrophysics Data System (ADS)

    Chen, Leanne D.; Noerskov, Jens K.; Luntz, Alan C.

    2015-03-01

    The Al-air battery possesses high theoretical specific energy (4140 Wh/kg) and is therefore an attractive candidate for vehicle propulsion applications. However, the experimentally observed open-circuit potential is much lower than what thermodynamics predicts, and this potential loss is widely believed to be an effect of corrosion. We present a detailed study of the Al-air battery using density functional theory. The results suggest that the difference between bulk thermodynamic and surface potentials is due to both the effects of asymmetry in multi-electron transfer reactions that define the anodic dissolution of Al and, more importantly, a large chemical step inherent to the formation of bulk Al(OH)3 from surface intermediates. The former results in an energy loss of 3%, while the latter accounts for 14 -29% of the total thermodynamic energy depending on the surface site where dissolution occurs. Therefore, the maximum open-circuit potential of the Al anode is only -1.87 V vs. SHE in the absence of thermal excitations, contrary to -2.34 V predicted by bulk thermodynamics at pH 14.6. This is a fundamental limitation of the system and governs the maximum output potential, which cannot be improved even if corrosion effects were completely suppressed. Supported by the Natural Sciences and Engineering Research Council of Canada and the ReLiable Project (#11-116792) funded by the Danish Council for Strategic Research.

  6. Design principles and limitations of wave-front guided contact lenses.

    PubMed

    Thibos, Larry N; Cheng, Xu; Bradley, Arthur

    2003-01-01

    The concept of the wave-front guided design of contact lenses is presented from three vantage points: ray optics, wave front aberrations, and optical path-length errors. We argue that the goal of contact lenses is to make all of the optical paths from a distant object to the retina equal in length, regardless of where the path intersects the plane of the eye's pupil. The aberration map of an eye is a prescription for such a lens. Unfortunately, variability of measured aberration maps is a fundamental limit to our knowledge of the true aberration structure of an eye. Variability arises because the eye is a biologic system that changes over time for normal, physiologic reasons. Furthermore, uncertainty in our measurement of the aberration map because of such variable factors, such as alignment of the aberrometer to the eye by the clinician or small fixation errors committed by the patient, will make it difficult to achieve a full measure of success with aberration-correcting contact lenses. The clinical implication of these findings is that multiple measurements of the aberration map should be collected using a protocol that includes realignment of the instrument and then averaging the aberration maps to reduce the level of uncertainty associated with any single measurement. PMID:12772758

  7. Al-Air Batteries: Fundamental Thermodynamic Limitations from First-Principles Theory.

    PubMed

    Chen, Leanne D; Nørskov, Jens K; Luntz, Alan C

    2015-01-01

    The Al-air battery possesses high theoretical specific energy (4140 W h/kg) and is therefore an attractive candidate for vehicle propulsion. However, the experimentally observed open-circuit potential is much lower than what bulk thermodynamics predicts, and this potential loss is typically attributed to corrosion. Similarly, large Tafel slopes associated with the battery are assumed to be due to film formation. We present a detailed thermodynamic study of the Al-air battery using density functional theory. The results suggest that the maximum open-circuit potential of the Al anode is only -1.87 V versus the standard hydrogen electrode at pH 14.6 instead of the traditionally assumed -2.34 V and that large Tafel slopes are inherent in the electrochemistry. These deviations from the bulk thermodynamics are intrinsic to the electrochemical surface processes that define Al anodic dissolution. This has contributions from both asymmetry in multielectron transfers and, more importantly, a large chemical stabilization inherent to the formation of bulk Al(OH)3 from surface intermediates. These are fundamental limitations that cannot be improved even if corrosion and film effects are completely suppressed. PMID:26263108

  8. Stable isotope fractionation to investigate natural transformation mechanisms of organic contaminants: principles, prospects and limitations.

    PubMed

    Elsner, Martin

    2010-11-01

    Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) has made it possible to analyze natural stable isotope ratios (e.g., (13)C/(12)C, (15)N/(14)N, (2)H/(1)H) of individual organic contaminants in environmental samples. They may be used as fingerprints to infer contamination sources, and may demonstrate, and even quantify, the occurrence of natural contaminant transformation by the enrichment of heavy isotopes that arises from degradation-induced isotope fractionation. This review highlights an additional powerful feature of stable isotope fractionation: the study of environmental transformation mechanisms. Isotope effects reflect the energy difference of isotopologues (i.e., molecules carrying a light versus a heavy isotope in a particular molecular position) when moving from reactant to transition state. Measuring isotope fractionation, therefore, essentially allows a glimpse at transition states! It is shown how such position-specific isotope effects are "diluted out" in the compound average measured by GC-IRMS, and how a careful evaluation in mechanistic scenarios and by dual isotope plots can recover the underlying mechanistic information. The mathematical framework for multistep isotope fractionation in environmental transformations is reviewed. Case studies demonstrate how isotope fractionation changes in the presence of mass transfer, enzymatic commitment to catalysis, multiple chemical reaction steps or limited bioavailability, and how this gives information about the individual process steps. Finally, it is discussed how isotope ratios of individual products evolve in sequential or parallel transformations, and what mechanistic insight they contain. A concluding session gives an outlook on current developments, future research directions and the potential for bridging the gap between laboratory and real world systems. PMID:21038038

  9. Closing the gap to the diffraction limit: Near wavelength limited tabletop soft x-ray coherent diffractive imaging

    NASA Astrophysics Data System (ADS)

    Sandberg, Richard Lunt

    Light microscopy has greatly advanced our understanding of nature. The achievable resolution, however, is limited by optical wavelengths to around 200 nm. Using novel imaging and labeling technologies, resolutions beyond the diffraction limit can be achieved for specialized specimens using techniques such as near-field scanning optical microscopy, stimulated emission depletion microscopy and structured illumination microscopy [1--3]. This dissertation presents a versatile soft x-ray diffraction microscope with 50 nm resolution using tabletop coherent soft x-ray sources. This work represents the first high resolution demonstrations of coherent diffractive or lensless imaging using tabletop extreme ultraviolet and soft x-ray sources [4, 5]. This dissertation also presents the first use of field curvature correction in x-ray coherent imaging which allows high numerical aperture imaging and near-diffraction-limited resolution of 1.5lambda. The relevant theory behind high harmonic generation, the primary tabletop source used in this work, will be discussed as well as the theory behind coherent diffractive imaging. Additionally, the first demonstration of tabletop soft x-ray Fourier Transform holography is shown with important applications to shorter wavelength imaging with high harmonic generation with limited flux. A tabletop soft x-ray diffraction microscope should find broad applications in biology, nanoscience, and materials science due to its simple optical design, high resolution, large depth of field, 3D imaging capability, scalability to shorter wavelengths, and ultrafast temporal resolution.

  10. First-principles AFM image simulation with frozen density embedding theory

    NASA Astrophysics Data System (ADS)

    Sakai, Yuki; Lee, Alex J.; Chelikowsky, James R.

    We present efficient first-principles method of non-contact atomic force microscopy (nc-AFM). Ordinary nc-AFM simulations based on density functional theory (DFT) require exhaustive computational cost because it involves thousands of total energy calculations. Regarding the sample as a fixed external potential can reduce the computational cost, and we adopt frozen density embedding theory (FDET) for this purpose. Simulated nc-AFM images with FDET using a carbon monoxide tip well reproduces the full DFT images of benzene, pentacene, and graphene, although optimized tip-sample distances and interaction energies in FDET are underestimated and overestimated, respectively. The FDET-based simulation method is promising for AFM image simulation of surfaces and two-dimensional materials. This work was supported by U.S. DOE under Grant No. DE-FG02-06ER46286 and Award No. DE-SC0008877, and by Welch Foundation under Grant F-1837. Computational resources are provided by NERSC and TACC.

  11. Principles and satellite applications of the information-efficient spectral imaging sensor

    SciTech Connect

    Stallard, B.R.; Gentry, S.M.; Sweatt, W.C.; Motomatsu, S.E.; Boye, C.A.

    1997-06-01

    Remote sensing by satellite is increasingly important to the national government for treaty verification, battlefield monitoring, and other activities. In addition, civilian oriented applications are increasing in areas such as geology, meteorology, ecology, forestry, and agriculture. Spectral imaging sensors, an important subclass of satellite-borne sensors, have been shown to provide information far superior to that of conventional panchromatic images in many of these applications. However, spectral imaging adds at least two challenges to the already difficult task of viewing the earth from a distance of hundreds of kilometers. First, with numerous spectral channels, the signal-to-noise ratio is decreased in any one channel. Second the data rates of spectral imaging sensors (10 Mbytes/sec, or more) stress the limits of the electronic systems, including the onboard data storage, the downlink bandwidth, and the earthbound image analysis system. This report describes a new concept which the authors have dubbed the information-efficient spectral imaging sensor (ISIS) which addresses these two problems. In addition, it offers the promise of nearly real-time identification of targets.

  12. An optical super-microscope for far-field, real-time imaging beyond the diffraction limit.

    PubMed

    Wong, Alex M H; Eleftheriades, George V

    2013-01-01

    Optical microscopy suffers from a fundamental resolution limitation arising from the diffractive nature of light. While current solutions to sub-diffraction optical microscopy involve combinations of near-field, non-linear and fine scanning operations, we hereby propose and demonstrate the optical super-microscope (OSM) - a superoscillation-based linear imaging system with far-field working and observation distances - which can image an object in real-time and with sub-diffraction resolution. With our proof-of-principle prototype we report a point spread function with a spot size clearly reduced from the diffraction limit, and demonstrate corresponding improvements in two-point resolution experiments. Harnessing a new understanding of superoscillations, based on antenna array theory, our OSM achieves far-field, sub-diffraction optical imaging of an object without the need for fine scanning, data post-processing or object pre-treatment. Hence the OSM can be used in a wide variety of imaging applications beyond the diffraction limit, including real-time imaging of moving objects. PMID:23612684

  13. An Optical Super-Microscope for Far-field, Real-time Imaging Beyond the Diffraction Limit

    PubMed Central

    Wong, Alex M. H.; Eleftheriades, George V.

    2013-01-01

    Optical microscopy suffers from a fundamental resolution limitation arising from the diffractive nature of light. While current solutions to sub-diffraction optical microscopy involve combinations of near-field, non-linear and fine scanning operations, we hereby propose and demonstrate the optical super-microscope (OSM) – a superoscillation-based linear imaging system with far-field working and observation distances – which can image an object in real-time and with sub-diffraction resolution. With our proof-of-principle prototype we report a point spread function with a spot size clearly reduced from the diffraction limit, and demonstrate corresponding improvements in two-point resolution experiments. Harnessing a new understanding of superoscillations, based on antenna array theory, our OSM achieves far-field, sub-diffraction optical imaging of an object without the need for fine scanning, data post-processing or object pre-treatment. Hence the OSM can be used in a wide variety of imaging applications beyond the diffraction limit, including real-time imaging of moving objects. PMID:23612684

  14. Limitations of using a thermal imager for snow pit temperatures

    NASA Astrophysics Data System (ADS)

    Schirmer, M.; Jamieson, B.

    2013-10-01

    Driven by temperature gradients, kinetic snow metamorphism is important for avalanche formation. Even when gradients appear to be insufficient for kinetic metamorphism, based on temperatures measured 10 cm apart, faceting close to a~crust can still be observed. Recent studies that visualized small scale (< 10 cm) thermal structures in a profile of snow layers with an infrared (IR) camera produced interesting results. The studies found melt-freeze crusts to be warmer or cooler than the surrounding snow depending on the large scale gradient direction. However, an important assumption within the studies was that a thermal photo of a freshly exposed snow pit was similar enough to the internal temperature of the snow. In this study, we tested this assumption by recording thermal videos during the exposure of the snow pit wall. In the first minute, the results showed increasing gradients with time, both at melt-freeze crusts and at artificial surface structures such as shovel scours. Cutting through a crust with a cutting blade or a shovel produced small concavities (holes) even when the objective was to cut a planar surface. Our findings suggest there is a surface structure dependency of the thermal image, which is only observed at times with large temperature differences between air and snow. We were able to reproduce the hot-crust/cold-crust phenomenon and relate it entirely to surface structure in a temperature-controlled cold laboratory. Concave areas cooled or warmed slower compared with convex areas (bumps) when applying temperature differences between snow and air. This can be explained by increased radiative transfer or convection by air at convex areas. Thermal videos suggest that such processes influence the snow temperature within seconds. Our findings show the limitations of the use of a thermal camera for measuring pit-wall temperatures, particularly in scenarios where large gradients exist between air and snow and the interaction of snow pit and

  15. Limitations of using a thermal imager for snow pit temperatures

    NASA Astrophysics Data System (ADS)

    Schirmer, M.; Jamieson, B.

    2014-03-01

    Driven by temperature gradients, kinetic snow metamorphism plays an import role in avalanche formation. When gradients based on temperatures measured 10 cm apart appear to be insufficient for kinetic metamorphism, faceting close to a crust can be observed. Recent studies that visualised small-scale (< 10 cm) thermal structures in a profile of snow layers with an infrared (IR) camera produced interesting results. The studies found melt-freeze crusts to be warmer or cooler than the surrounding snow depending on the large-scale gradient direction. However, an important assumption within these studies was that a thermal photo of a freshly exposed snow pit was similar enough to the internal temperature of the snow. In this study, we tested this assumption by recording thermal videos during the exposure of the snow pit wall. In the first minute, the results showed increasing gradients with time, both at melt-freeze crusts and artificial surface structures such as shovel scours. Cutting through a crust with a cutting blade or shovel produced small concavities (holes) even when the objective was to cut a planar surface. Our findings suggest there is a surface structure dependency of the thermal image, which was only observed at times during a strong cooling/warming of the exposed pit wall. We were able to reproduce the hot-crust/cold-crust phenomenon and relate it entirely to surface structure in a temperature-controlled cold laboratory. Concave areas cooled or warmed more slowly compared with convex areas (bumps) when applying temperature differences between snow and air. This can be explained by increased radiative and/or turbulent energy transfer at convex areas. Thermal videos suggest that such processes influence the snow temperature within seconds. Our findings show the limitations of using a thermal camera for measuring pit-wall temperatures, particularly during windy conditions, clear skies and large temperature differences between air and snow. At crusts or other

  16. IMAGING THE EPOCH OF REIONIZATION: LIMITATIONS FROM FOREGROUND CONFUSION AND IMAGING ALGORITHMS

    SciTech Connect

    Vedantham, Harish; Udaya Shankar, N.; Subrahmanyan, Ravi

    2012-02-01

    Tomography of redshifted 21 cm transition from neutral hydrogen using Fourier synthesis telescopes is a promising tool to study the Epoch of Reionization (EoR). Limiting the confusion from Galactic and extragalactic foregrounds is critical to the success of these telescopes. The instrumental response or the point-spread function (PSF) of such telescopes is inherently three dimensional with frequency mapping to the line-of-sight (LOS) distance. EoR signals will necessarily have to be detected in data where continuum confusion persists; therefore, it is important that the PSF has acceptable frequency structure so that the residual foreground does not confuse the EoR signature. This paper aims to understand the three-dimensional PSF and foreground contamination in the same framework. We develop a formalism to estimate the foreground contamination along frequency, or equivalently LOS dimension, and establish a relationship between foreground contamination in the image plane and visibility weights on the Fourier plane. We identify two dominant sources of LOS foreground contamination-'PSF contamination' and 'gridding contamination'. We show that PSF contamination is localized in LOS wavenumber space, beyond which there potentially exists an 'EoR window' with negligible foreground contamination where we may focus our efforts to detect EoR. PSF contamination in this window may be substantially reduced by judicious choice of a frequency window function. Gridding and imaging algorithms create additional gridding contamination and we propose a new imaging algorithm using the Chirp Z Transform that significantly reduces this contamination. Finally, we demonstrate the analytical relationships and the merit of the new imaging algorithm for the case of imaging with the Murchison Widefield Array.

  17. Body diffusion kurtosis imaging: Basic principles, applications, and considerations for clinical practice.

    PubMed

    Rosenkrantz, Andrew B; Padhani, Anwar R; Chenevert, Thomas L; Koh, Dow-Mu; De Keyzer, Frederik; Taouli, Bachir; Le Bihan, Denis

    2015-11-01

    Technologic advances enable performance of diffusion-weighted imaging (DWI) at ultrahigh b-values, where standard monoexponential model analysis may not apply. Rather, non-Gaussian water diffusion properties emerge, which in cellular tissues are, in part, influenced by the intracellular environment that is not well evaluated by conventional DWI. The novel technique, diffusion kurtosis imaging (DKI), enables characterization of non-Gaussian water diffusion behavior. More advanced mathematical curve fitting of the signal intensity decay curve using the DKI model provides an additional parameter Kapp that presumably reflects heterogeneity and irregularity of cellular microstructure, as well as the amount of interfaces within cellular tissues. Although largely applied for neural applications over the past decade, a small number of studies have recently explored DKI outside the brain. The most investigated organ is the prostate, with preliminary studies suggesting improved tumor detection and grading using DKI. Although still largely in the research phase, DKI is being explored in wider clinical settings. When assessing extracranial applications of DKI, careful attention to details with which body radiologists may currently be unfamiliar is important to ensure reliable results. Accordingly, a robust understanding of DKI is necessary for radiologists to better understand the meaning of DKI-derived metrics in the context of different tumors and how these metrics vary between tumor types and in response to treatment. In this review, we outline DKI principles, propose biostructural basis for observations, provide a comparison with standard monoexponential fitting and the apparent diffusion coefficient, report on extracranial clinical investigations to date, and recommend technical considerations for implementation in body imaging. PMID:26119267

  18. [(18)F]-Organotrifluoroborates as Radioprosthetic Groups for PET Imaging: From Design Principles to Preclinical Applications.

    PubMed

    Perrin, David M

    2016-07-19

    Positron emission tomography (PET) is revolutionizing our ability to visualize in vivo targets for target validation and personalized medicine. Of several classes of imaging agents, peptides afford high affinity and high specificity to distinguish pathologically distinct cell types by the presence of specific molecular targets. Of various available PET isotopes, [(18)F]-fluoride ion is preferred because of its excellent nuclear properties and on-demand production in hospitals at Curie levels. However, the short half-life of (18)F and its lack of reactivity in water continue to challenge peptide labeling. Hence, peptides are often conjugated to a metal chelator for late-stage, one-step labeling. Yet radiometals, while effective, are neither as desirable nor as available as [(18)F]-fluoride ion. Despite considerable past success in identifying semifeasible radiosyntheses, significant challenges continue to confound tracer development. These interrelated challenges relate to (1) isotope/prosthetic choice; (2) bioconjugation for high affinity; (3) high radiochemical yields, (4) specific activities of >1 Ci/μmol to meet FDA microdose requirements; and (5) rapid clearance and in vivo stability. These enduring challenges have been extensively highlighted, while a single-step, operationally simple, and generally applicable means of labeling a peptide with [(18)F]-fluoride ion in good yield and high specific activity has eluded radiochemists and nuclear medicine practitioners for decades. Radiosynthetic ease is of primordial importance since multistep labeling reactions challenge clinical tracer production. In the past decade, as we sought to meet this challenge, appreciation of reactions with aqueous fluoride led us to consider organotrifluoroborate (RBF3(-)) synthesis as a means of rapid aqueous peptide labeling. We have applied principles of mechanistic chemistry, knowledge of chemical reactivity, and synthetic chemistry to design stable RBF3(-)s. Over the past 10 years

  19. Book review of "Biomagnetics: Principles and Applications of Biomagnetic Stimulation and Imaging" edited by Shoogo Ueno and Masaki Sekino.

    PubMed

    Riu, Pere J

    2016-01-01

    This article is a review of the book "Biomagnetics: Principles and Applications of Biomagnetic Stimulation and Imaging" (ISBN 978-1-4822-3920-1, 343 pages) edited by Shoogo Ueno and Masaki Sekino published by CRC Press, Taylor and Francis Group, LLC in 2015. The content of the book and its importance for biomedical engineering have been discussed in this invited review. PMID:27176038

  20. Ultrasound contrast microbubbles in imaging and therapy: physical principles and engineering

    PubMed Central

    Qin, Shengping; Caskey, Charles F; Ferrara, Katherine W

    2010-01-01

    Microbubble contrast agents and the associated imaging systems have developed over the past twenty-five years, originating with manually-agitated fluids introduced for intra-coronary injection. Over this period, stabilizing shells and low diffusivity gas materials have been incorporated in microbubbles, extending stability in vitro and in vivo. Simultaneously, the interaction of these small gas bubbles with ultrasonic waves has been extensively studied, resulting in models for oscillation and increasingly sophisticated imaging strategies. Early studies recognized that echoes from microbubbles contained frequencies that are multiples of the microbubble resonance frequency. Although individual microbubble contrast agents cannot be resolved—given that their diameter is on the order of microns—nonlinear echoes from these agents are used to map regions of perfused tissue and to estimate the local microvascular flow rate. Such strategies overcome a fundamental limitation of previous ultrasound blood flow strategies; the previous Doppler-based strategies are insensitive to capillary flow. Further, the insonation of resonant bubbles results in interesting physical phenomena that have been widely studied for use in drug and gene delivery. Ultrasound pressure can enhance gas diffusion, rapidly fragment the agent into a set of smaller bubbles or displace the microbubble to a blood vessel wall. Insonation of a microbubble can also produce liquid jets and local shear stress that alter biological membranes and facilitate transport. In this review, we focus on the physical aspects of these agents, exploring microbubble imaging modes, models for microbubble oscillation and the interaction of the microbubble with the endothelium. PMID:19229096

  1. TOPICAL REVIEW: Ultrasound contrast microbubbles in imaging and therapy: physical principles and engineering

    NASA Astrophysics Data System (ADS)

    Qin, Shengping; Caskey, Charles F.; Ferrara, Katherine W.

    2009-03-01

    Microbubble contrast agents and the associated imaging systems have developed over the past 25 years, originating with manually-agitated fluids introduced for intra-coronary injection. Over this period, stabilizing shells and low diffusivity gas materials have been incorporated in microbubbles, extending stability in vitro and in vivo. Simultaneously, the interaction of these small gas bubbles with ultrasonic waves has been extensively studied, resulting in models for oscillation and increasingly sophisticated imaging strategies. Early studies recognized that echoes from microbubbles contained frequencies that are multiples of the microbubble resonance frequency. Although individual microbubble contrast agents cannot be resolved—given that their diameter is on the order of microns—nonlinear echoes from these agents are used to map regions of perfused tissue and to estimate the local microvascular flow rate. Such strategies overcome a fundamental limitation of previous ultrasound blood flow strategies; the previous Doppler-based strategies are insensitive to capillary flow. Further, the insonation of resonant bubbles results in interesting physical phenomena that have been widely studied for use in drug and gene delivery. Ultrasound pressure can enhance gas diffusion, rapidly fragment the agent into a set of smaller bubbles or displace the microbubble to a blood vessel wall. Insonation of a microbubble can also produce liquid jets and local shear stress that alter biological membranes and facilitate transport. In this review, we focus on the physical aspects of these agents, exploring microbubble imaging modes, models for microbubble oscillation and the interaction of the microbubble with the endothelium.

  2. Conventional transmission electron microscopy imaging beyond the diffraction and information limits.

    PubMed

    Rosenauer, Andreas; Krause, Florian F; Müller, Knut; Schowalter, Marco; Mehrtens, Thorsten

    2014-08-29

    There are mainly two complementary imaging modes in transmission electron microscopy (TEM): Conventional TEM (CTEM) and scanning TEM (STEM). In the CTEM mode the specimen is illuminated with a plane electron wave, and the direct image formed by the objective lens is recorded in the image plane. STEM is based on scanning the specimen surface with a focused electron beam and collecting scattered electrons with an extended disk or ring-shaped detector. Here we show that combination of CTEM imaging with STEM illumination generally allows extending the point resolution of CTEM imaging beyond the diffraction limit. This new imaging mode improves imaging characteristics, is more robust against chromatic aberration, exhibits direct structural imaging with superior precision, visualizes light elements with excellent contrast, and even allows us to overcome the conventional information limit of a microscope. PMID:25215995

  3. Limitation on image resolution imposed by a random medium.

    PubMed

    Ishimaru, A

    1978-02-01

    In underwater photography, it was reported that clear photographs were obtained through water with large (10-15) optical distances even though the MTF rolls off at a few cycles per mrad. This paper presents an explanation of this apparent contradiction by showing that at a large optical distance where the total coherent intensity is negligibly small compared with the total incoherent intensity, it is still possible to form the Airy disk due to the coherent intensity. We present the condition under which this can take place and applied the results to an imaging system in still water and in water with particulate matter. PMID:20174413

  4. Band-Limited Masks and Direct Imaging of Exoplanets

    NASA Technical Reports Server (NTRS)

    Kuchner, Marc J.

    2009-01-01

    Band-limited masks have become the baseline design for what is now called "classical TPF" and also the N|RCamcomnagraphonJW8 .This technology remains one of the most promising paths for direct detection ofmxop|anedm and disks. I'll describe some of the latest progress in the implementation of this technique and what we have learned about where it can and can not be effectively applied.

  5. Passive synthetic aperture imaging with limited noise sources

    NASA Astrophysics Data System (ADS)

    Garnier, Josselin

    2016-09-01

    We consider a passive synthetic aperture imaging problem. A single moving receiver antenna records random signals generated by one or several distant noise sources and backscattered by one or several reflectors. The sources emit noise signals modeled by stationary random processes. The reflectors can be imaged by summing the autocorrelation functions of the received signals computed over successive time windows, corrected for Doppler factors and migrated by appropriate travel times. In particular, the Doppler effect plays an important role and it can be used for resolution enhancement. When the noise source positions are not known, the reflector can be localized with an accuracy proportional to the reciprocal of the noise bandwidth, even when only a very small number of sources are available. When the noise source positions are known, the reflector can be localized with a cross range resolution proportional to the carrier wavelength and inversely proportional to the length of the receiver trajectory (i.e. the synthetic aperture), and with a range resolution proportional to the reciprocal of the bandwidth, even with only one noise source.

  6. Phase errors in diffraction-limited imaging: contrast limits for sparse aperture masking

    NASA Astrophysics Data System (ADS)

    Ireland, M. J.

    2013-08-01

    Bispectrum phase, closure phase and their generalization to kernel phase are all independent of pupil-plane phase errors to first order. This property, when used with sparse aperture masking behind adaptive optics, has been used recently in high-contrast observations at or inside the formal diffraction limit of large telescopes. Finding the limitations to these techniques requires an understanding of spatial and temporal third-order phase effects, as well as effects such as time-variable dispersion when coupled with the non-zero bandwidths in real observations. In this paper, formulae describing many of these errors are developed, so that a comparison can be made to fundamental noise processes of photon noise and background noise. I show that the current generation of aperture-masking observations of young solar-type stars, taken carefully in excellent observing conditions, are consistent with being limited by temporal phase noise and photon noise. This has relevance for plans to combine pupil remapping with spatial filtering. Finally, I describe calibration strategies for kernel phase, including the optimized calibrator weighting as used for LkCa15, and the restricted kernel phase POISE (phase observationally independent of systematic errors) technique that avoids explicit dependence on calibrators.

  7. [Ultrasound imaging of the anterior cruciate ligament. Possibilities and limits].

    PubMed

    Kelsch, G; Ulrich, C; Bickelhaupt, A

    1996-02-01

    We carried out sonography of the femoral origin of the anterior cruciate ligament in the dorsal cross section with a 7.5-MHz linear scanner in 25 test subjects with healthy knee joints. A physiological difference between the sides in the size of the hypoechoic region of the origin could be defined on the basis of the measurements obtained in both knee joints. Values outside a reference range which could be evaluated from this difference were rated as pathological in terms of an anterior cruciate ligament rupture. The reliability of this method in definitively diagnosing an anterior cruciate ligament rupture was analysed statistically as compared to the golden standard of arthroscopy on 65 patients by means of the two-by-two frequency table test. The femoral origin of the cruciate ligament in 25 test subjects had a median width of 3.1 mm (range 1.7-5.8 mm) on the right and 3.4 mm (range 1.7-4.4 mm) on the left. The median difference between the sides is 0.4 mm (range 0-1.8 mm). If the 3rd to the 97th percentile is selected as the reference range, our data show a physiological difference between the sides of 0-1.5 mm. The median age of the 65 patients was 31 years (range 14-74 years). Two thirds of all patients were men. A rupture of the anterior cruciate ligament was diagnosed sonographically in 19 patients. The result was confirmed arthroscopically in 15 patients. In 4 patients, there was a false positive sonographic finding. Forty-six patients did not fulfil the sonographic criteria of a rupture of the anterior cruciate ligament. Of these, 38 showed an intact anterior cruciate ligament on arthroscopy. Eight patients had a false-negative sonographic finding. The corresponding statistical analysis showed sensitivity of 65%, specificity of 90% and precision of 79%. Accordingly, the diagnostic reliability of knee joint sonography in diagnosing a rupture of the anterior cruciate ligament appears to be unsatisfactory, since old ruptures, above all, cannot be imaged with

  8. Limiter

    DOEpatents

    Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.

    1984-10-19

    A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.

  9. Covariance of lucky images for increasing objects contrast: diffraction-limited images in ground-based telescopes

    NASA Astrophysics Data System (ADS)

    Cagigal, Manuel P.; Valle, Pedro J.; Colodro-Conde, Carlos; Villó-Pérez, Isidro; Pérez-Garrido, Antonio

    2016-01-01

    Images of stars adopt shapes far from the ideal Airy pattern due to atmospheric density fluctuations. Hence, diffraction-limited images can only be achieved by telescopes without atmospheric influence, e.g. spatial telescopes, or by using techniques like adaptive optics or lucky imaging. In this paper, we propose a new computational technique based on the evaluation of the COvariancE of Lucky Images (COELI). This technique allows us to discover companions to main stars by taking advantage of the atmospheric fluctuations. We describe the algorithm and we carry out a theoretical analysis of the improvement in contrast. We have used images taken with 2.2-m Calar Alto telescope as a test bed for the technique resulting that, under certain conditions, telescope diffraction limit is clearly reached.

  10. In vitro and in vivo real-time imaging with ultrasonic limited diffraction beams.

    PubMed

    Lu, J Y; Song, T K; Kinnick, R R; Greenleaf, J F

    1993-01-01

    Recently, there has been great interest in a new class of solutions to the isotropic/homogeneous scaler wave equation which represents localized waves or limited diffraction beams in electromagnetics, optics, and acoustics. Applications of these solutions to ultrasonic medical imaging, tissue characterization, and nondestructive evaluation of materials have also been reported. The authors report a real-time medical imager which uses limited diffraction Bessel beams, X-waves, Axicons, or conventional beams. Results (in vitro and in vivo) show that the images obtained with limited diffraction beams have higher resolution and good contrast over larger depth of field compared to images obtained with conventional focused beams. These results suggest the potential clinical usefulness of limited diffraction beams. PMID:18218478

  11. Milestones and basic principles of grating-based x-ray and neutron phase-contrast imaging

    SciTech Connect

    Pfeiffer, Franz

    2012-07-31

    This is a review of the most important milestones in the last ten years of development in the field of grating-based x-ray and neutron imaging. It provides a description of the basic imaging principles of grating-based phase-contrast and dark-field radiography and present some exemplary multimodal radiography results obtained with x-rays and neutrons. Furthermore, it reviews the theory of grating-based quantitative transmission, phase-contrast, and dark-field scattering computed tomography.

  12. Breaking the acoustic diffraction limit in photoacoustic imaging with multiple speckle illumination

    NASA Astrophysics Data System (ADS)

    Chaigne, Thomas; Gateau, Jérôme; Allain, Marc; Katz, Ori; Gigan, Sylvain; Sentenac, Anne; Bossy, Emmanuel

    2016-03-01

    In deep photoacoustic imaging, resolution is inherently limited by acoustic diffraction, and ultrasonic frequencies cannot be arbitrarily increased because of attenuation in tissue. Here we report on the use of multiple speckle illumination to perform super resolution photoacoustic imaging. We show that the analysis of speckle-induced second-order fluctuations of the photoacoustic signal combined with deconvolution enables to resolve optically absorbing structures below the acoustic diffraction limit.

  13. Limited-view light sheet fluorescence microscopy for three dimensional volume imaging

    NASA Astrophysics Data System (ADS)

    Rasmi, C. K.; Mohan, Kavya; Madhangi, M.; Rajan, K.; Nongthomba, U.; Mondal, Partha P.

    2015-12-01

    We propose and demonstrate a limited-view light sheet microscopy (LV-LSM) for three dimensional (3D) volume imaging. Realizing that longer and frequent image acquisition results in significant photobleaching, we have taken limited angular views (18 views) of the macroscopic specimen and integrated with maximum likelihood (ML) technique for reconstructing high quality 3D volume images. Existing variants of light-sheet microscopy require both rotation and translation with a total of approximately 10-fold more views to render a 3D volume image. Comparatively, LV-LSM technique reduces data acquisition time and consequently minimizes light-exposure by many-folds. Since ML is a post-processing technique and highly parallelizable, this does not cost precious imaging time. Results show noise-free and high contrast volume images when compared to the state-of-the-art selective plane illumination microscopy.

  14. Limiter

    DOEpatents

    Cohen, Samuel A.; Hosea, Joel C.; Timberlake, John R.

    1986-01-01

    A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.

  15. Wavefront curvature limitations and compensation to polar format processing for synthetic aperture radar images.

    SciTech Connect

    Doerry, Armin Walter

    2006-01-01

    Limitations on focused scene size for the Polar Format Algorithm (PFA) for Synthetic Aperture Radar (SAR) image formation are derived. A post processing filtering technique for compensating the spatially variant blurring in the image is examined. Modifications to this technique to enhance its robustness are proposed.

  16. Medical Imaging.

    ERIC Educational Resources Information Center

    Jaffe, C. Carl

    1982-01-01

    Describes principle imaging techniques, their applications, and their limitations in terms of diagnostic capability and possible adverse biological effects. Techniques include film radiography, computed tomography, nuclear medicine, positron emission tomography (PET), ultrasonography, nuclear magnetic resonance, and digital radiography. PET has…

  17. ℓ0 Gradient Minimization Based Image Reconstruction for Limited-Angle Computed Tomography

    PubMed Central

    Yu, Wei; Zeng, Li

    2015-01-01

    In medical and industrial applications of computed tomography (CT) imaging, limited by the scanning environment and the risk of excessive X-ray radiation exposure imposed to the patients, reconstructing high quality CT images from limited projection data has become a hot topic. X-ray imaging in limited scanning angular range is an effective imaging modality to reduce the radiation dose to the patients. As the projection data available in this modality are incomplete, limited-angle CT image reconstruction is actually an ill-posed inverse problem. To solve the problem, image reconstructed by conventional filtered back projection (FBP) algorithm frequently results in conspicuous streak artifacts and gradual changed artifacts nearby edges. Image reconstruction based on total variation minimization (TVM) can significantly reduce streak artifacts in few-view CT, but it suffers from the gradual changed artifacts nearby edges in limited-angle CT. To suppress this kind of artifacts, we develop an image reconstruction algorithm based on ℓ0 gradient minimization for limited-angle CT in this paper. The ℓ0-norm of the image gradient is taken as the regularization function in the framework of developed reconstruction model. We transformed the optimization problem into a few optimization sub-problems and then, solved these sub-problems in the manner of alternating iteration. Numerical experiments are performed to validate the efficiency and the feasibility of the developed algorithm. From the statistical analysis results of the performance evaluations peak signal-to-noise ratio (PSNR) and normalized root mean square distance (NRMSD), it shows that there are significant statistical differences between different algorithms from different scanning angular ranges (p<0.0001). From the experimental results, it also indicates that the developed algorithm outperforms classical reconstruction algorithms in suppressing the streak artifacts and the gradual changed artifacts nearby edges

  18. On three new principles in non-equilibrium statistical mechanics and Markov semigroups of weak coupling limit type

    NASA Astrophysics Data System (ADS)

    Accardi, Luigi; Fagnola, Franco; Quezada, Roberto

    2016-06-01

    We introduce three new principles: the nonlinear Boltzmann-Gibbs prescription, the local KMS condition and the generalized detailed balance (GDB) condition. We prove the equivalence of the first two under general conditions and we discuss a master equation formulation of the third one.

  19. Lensfree on-chip high-resolution imaging using two-way lighting, and its limitations

    NASA Astrophysics Data System (ADS)

    Adachi, Yasuhiko; Tamaki, Tokuhiko; Motomura, Hideto; Kato, Yoshihisa

    2016-03-01

    A high-magnification image of a biological sample can generally be obtained by an optical microscope with an objective lens, moving the image sensor with a sub-pixel shift and the subsequent image processing for super-resolution. However, to obtain a high-resolution image, a large number of images will be required for the super-resolution, and thus it is difficult to achieve real-time operation, and the field-of-view (FOV) is not sufficiently wide. The currently proposed digital holography technique places a sample on the image sensor and captures the interference fringe (hologram) to reconstruct a 3D high-resolution image in a computer. This technique ensures the features of a wide FOV, whereas the high resolution obtained by image processing cannot ensure real-time operation, because it requires recursive calculations of light propagation and adequate computer resources. To realize wide FOV and the real-time operation at the same time, we have developed a new technique: Lensfree on-chip high-resolution imaging using two-way lighting. High-resolution image is immediately obtained by image processing of the low-resolution images of the samples. This makes it possible to ensure a wide FOV, a deep depth of focus without the need for focus adjustment, and a continuously expanding operation. We also discuss the limitations of the high resolution.

  20. The Adaptive Optics Lucky Imager: Diffraction limited imaging at visible wavelengths with large ground-based telescopes

    NASA Astrophysics Data System (ADS)

    Crass, Jonathan; Mackay, Craig; King, David; Rebolo-López, Rafael; Labadie, Lucas; Puga, Marta; Oscoz, Alejandro; González Escalera, Victor; Pérez Garrido, Antonio; López, Roberto; Pérez-Prieto, Jorge; Rodríguez-Ramos, Luis; Velasco, Sergio; Villó, Isidro

    2015-01-01

    One of the continuing challenges facing astronomers today is the need to obtain ever higher resolution images of the sky. Whether studying nearby crowded fields or distant objects, with increased resolution comes the ability to probe systems in more detail and advance our understanding of the Universe. Obtaining these high-resolution images at visible wavelengths however has previously been limited to the Hubble Space Telescope (HST) due to atmospheric effects limiting the spatial resolution of ground-based telescopes to a fraction of their potential. With HST now having a finite lifespan, it is prudent to investigate other techniques capable of providing these kind of observations from the ground. Maintaining this capability is one of the goals of the Adaptive Optics Lucky Imager (AOLI).Achieving the highest resolutions requires the largest telescope apertures, however, this comes at the cost of increased atmospheric distortion. To overcome these atmospheric effects, there are two main techniques employed today: adaptive optics (AO) and lucky imaging. These techniques individually are unable to provide diffraction limited imaging in the visible on large ground-based telescopes; AO currently only works at infrared wavelengths while lucky imaging reduces in effectiveness on telescopes greater than 2.5 metres in diameter. The limitations of both techniques can be overcome by combing them together to provide diffraction limited imaging at visible wavelengths on the ground.The Adaptive Optics Lucky Imager is being developed as a European collaboration and combines AO and lucky imaging in a dedicated instrument for the first time. Initially for use on the 4.2 metre William Herschel Telescope, AOLI uses a low-order adaptive optics system to reduce the effects of atmospheric turbulence before imaging with a lucky imaging based science detector. The AO system employs a novel type of wavefront sensor, the non-linear Curvature Wavefront Sensor (nlCWFS) which provides

  1. Cost-appropriateness of whole body vs limited bone imaging for suspected focal sports injuries

    SciTech Connect

    Nagle, C.E.

    1986-07-01

    Bone imaging has been recognized as a useful diagnostic tool in detecting the presence of focal musculoskeletal injury when radiographs are normal. A retrospective review of bone images in a small number of amateur athletes indicates that secondary injuries were commonly detected at sites different from the site of musculoskeletal pain being evaluated for injury. While a larger study will be necessary to confirm the data, this review suggests that it is medically justified and cost-appropriate to perform imaging of the entire skeleton as opposed to imaging limited to the anatomic site of pain and suspected injury.

  2. X-ray phase sensitive imaging methods: basic physical principles and potential medical applications

    PubMed Central

    Chen, Guang-Hong; Zambelli, Joseph; Bevins, Nicholas; Qi, Zhihua; Li, Ke

    2013-01-01

    Phase sensitive imaging theoretically allows for a drastic reduction in x-ray dose while simultaneously achieving comparable or better spatial and contrast resolution compared to traditional x-ray absorption based imaging. Several techniques exist to extract the phase information from an x-ray signal, including x-ray interferometry, diffraction enhanced imaging, in-line holography, coded aperture x-ray imaging, and grating-based interferometry. The physics of each method is reviewed, along with the potential clinical applications. PMID:23970846

  3. Image contrast of diffraction-limited telescopes for circular incoherent sources of uniform radiance

    NASA Technical Reports Server (NTRS)

    Shackleford, W. L.

    1980-01-01

    A simple approximate formula is derived for the background intensity beyond the edge of the image of uniform incoherent circular light source relative to the irradiance near the center of the image. The analysis applies to diffraction-limited telescopes with or without central beam obscuration due to a secondary mirror. Scattering off optical surfaces is neglected. The analysis is expected to be most applicable to spaceborne IR telescopes, for which diffraction can be the major source of off-axis response.

  4. Mapping Atomic Orbitals with the Transmission Electron Microscope: Images of Defective Graphene Predicted from First-Principles Theory

    NASA Astrophysics Data System (ADS)

    Pardini, Lorenzo; Löffler, Stefan; Biddau, Giulio; Hambach, Ralf; Kaiser, Ute; Draxl, Claudia; Schattschneider, Peter

    2016-07-01

    Transmission electron microscopy has been a promising candidate for mapping atomic orbitals for a long time. Here, we explore its capabilities by a first-principles approach. For the example of defected graphene, exhibiting either an isolated vacancy or a substitutional nitrogen atom, we show that three different kinds of images are to be expected, depending on the orbital character. To judge the feasibility of visualizing orbitals in a real microscope, the effect of the optics' aberrations is simulated. We demonstrate that, by making use of energy filtering, it should indeed be possible to map atomic orbitals in a state-of-the-art transmission electron microscope.

  5. Mapping Atomic Orbitals with the Transmission Electron Microscope: Images of Defective Graphene Predicted from First-Principles Theory.

    PubMed

    Pardini, Lorenzo; Löffler, Stefan; Biddau, Giulio; Hambach, Ralf; Kaiser, Ute; Draxl, Claudia; Schattschneider, Peter

    2016-07-15

    Transmission electron microscopy has been a promising candidate for mapping atomic orbitals for a long time. Here, we explore its capabilities by a first-principles approach. For the example of defected graphene, exhibiting either an isolated vacancy or a substitutional nitrogen atom, we show that three different kinds of images are to be expected, depending on the orbital character. To judge the feasibility of visualizing orbitals in a real microscope, the effect of the optics' aberrations is simulated. We demonstrate that, by making use of energy filtering, it should indeed be possible to map atomic orbitals in a state-of-the-art transmission electron microscope. PMID:27472127

  6. Research on the principle and experimentation of optical compressive spectral imaging

    NASA Astrophysics Data System (ADS)

    Chen, Yuheng; Chen, Xinhua; Zhou, Jiankang; Ji, Yiqun; Shen, Weimin

    2013-12-01

    The optical compressive spectral imaging method is a novel spectral imaging technique that draws in the inspiration of compressed sensing, which takes on the advantages such as reducing acquisition data amount, realizing snapshot imaging, increasing signal to noise ratio and so on. Considering the influence of the sampling quality on the ultimate imaging quality, researchers match the sampling interval with the modulation interval in former reported imaging system, while the depressed sampling rate leads to the loss on the original spectral resolution. To overcome that technical defect, the demand for the matching between the sampling interval and the modulation interval is disposed of and the spectral channel number of the designed experimental device increases more than threefold comparing to that of the previous method. Imaging experiment is carried out by use of the experiment installation and the spectral data cube of the shooting target is reconstructed with the acquired compressed image by use of the two-step iterative shrinkage/thresholding algorithms. The experimental result indicates that the spectral channel number increases effectively and the reconstructed data stays high-fidelity. The images and spectral curves are able to accurately reflect the spatial and spectral character of the target.

  7. Far-field imaging beyond diffraction limit using single sensor in combination with a resonant aperture.

    PubMed

    Li, Lianlin; Li, Fang; Cui, Tie Jun; Yao, Kan

    2015-01-12

    Far-field imaging beyond the diffraction limit is a long sought-after goal in various imaging applications, which requires usually mechanical scanning or an array of antennas. Here, we propose to solve this challenging problem using a single sensor in combination with a spatio-temporal resonant aperture antenna. We theoretically and numerically demonstrate that such resonant aperture antenna is capable of converting part evanescent waves into propagating waves and delivering them to far fields. The proposed imaging concept provides the unique ability to achieve super resolution for real-time data when illuminated by broadband electromagnetic waves, without the harsh requirements such as near- field scanning, mechanical scanning, or antenna arrays. We expect the imaging methodology to make breakthroughs in super-resolution imaging in microwave, terahertz, optical, and ultrasound regimes. PMID:25835685

  8. Limits of imaging-system simplification using cubic mask wavefront coding.

    PubMed

    Larivière-Bastien, Martin; Thibault, Simon

    2013-10-01

    Increasing the space-bandwidth product of an imaging system will lead to a complex and expensive optical system. Techniques exist to simplify imaging systems. We propose the use of a hybrid imaging system using pupil phase modulation. Based on the reconstructed image's mean-squared error, we compute how this error is affected under various third-order aberrations. We determine the best cubic phase-mask parameter and study the impact of the orientation of the coma and astigmatism, as we have in a real optical system (from 0 to 2π). We then compute how the reconstructed image's quality varies by adding defocus-related aberrations (defocus and/or field curvature). Based on our analysis, we determine the limits of a hybrid imaging system using a cubic phase mask to develop simplified imaging systems. We conclude that the simplified lens design can be corrected if its aberrations are limited to 1 lambda of coma, astigmatism, and spherical aberrations and less than 1 lambda of field curvature or defocus. PMID:24081064

  9. Iterative image reconstruction for limited-angle inverse helical cone-beam computed tomography.

    PubMed

    Yu, Wei; Zeng, Li

    2016-01-01

    Helical trajectory satisfying the condition of exact reconstruction, has been widely utilized in the commercial computed tomography (CT). While limited by the scanning environment in some practical applications, the conventional helical cone-beam CT imaging is hard to complete, thus, developing an imaging system suited for long-object may be valuable. Three-dimensional C-arm CT is an innovative imaging technique which has been greatly concerned. Since there is a high degree of freedom of C-arm, more flexible image acquisition trajectories for 3D imaging can be achieved. In this work, a fast iterative reconstruction algorithm based on total variation minimization is developed for a trajectory of limited-angle inverse helical cone-beam CT, which can be applied to detect long-object without slip-ring technology. The experimental results show that the developed algorithm can yield reconstructed images of low noise level and high image quality. SCANNING 38:4-13, 2016. © 2015 Wiley Periodicals, Inc. PMID:26130367

  10. Proof of principle for helmet-mounted display image quality tester

    NASA Astrophysics Data System (ADS)

    Hsieh, Sheng-Jen; Harding, Thomas H.; Rash, Clarence E.; Beasley, Howard H.; Martin, John S.

    2003-09-01

    Helmet mounted displays (HMDs) provide essential pilotage and fire control imagery information for pilots. To maintain system integrity and readiness, there is a need to develop an image quality-testing tool for HMDs. There is currently no such tool. A framework for development of an image quality tester for the Integrated Helmet and Display Sighting System (IHADSS) used in the U.S. Army's AH-64 was proposed in Hsieh et al. This paper presents the prototype development, summarizes the bench test findings using three IHADSS helmet display units (HDUs), and concludes with recommendations for future directions. The prototype consists of hardware (two cameras, sensors, image capture/data acquisition cards, battery pack, HDU holder, moveable rack and handle, and computer) and software algorithms for image capture and analysis. Two cameras with different apertures were mounted in parallel on a rack facing the HDU holder. A handle was designed to allow users to position the HDU in front of the two cameras. The HMD test pattern was then captured. Sensors are used to detect the position of the holder and whether the HDU was angled correctly in relation to the camera. Two sets of unified algorithms were designed to detect features presented by the two cameras. These features include focus, orientation, displacement, field-of-view, and number of gray-shades. Images of test pattern were captured and analyzed, and used to develop a specification for each inspection feature. Experiments were conducted to verify the robustness of the algorithms. A worst-case scenario for factors such as clock-wise and counterclockwise tilt, degree of focus, magnitude of brightness and contrast, and shifted images were set up and evaluated. Bench testing of three field-quality HDUs indicate that the image analysis algorithms are robust and able to detect the desired image features. Suggested future work includes development of a learning algorithm to automatically develop or revise feature

  11. First-principles study of crystalline silicon hyperdoped with cobalt at a concentration exceeding the Mott limit

    NASA Astrophysics Data System (ADS)

    Dong, Xiao; Wang, Yongyong; Song, Xiaohui; Wang, Jinfeng; Li, Xueping

    2016-07-01

    We systematically studied the properties of Co-hyperdoped silicon using first-principles calculations based on density-functional theory. A series of more complex configurations, such as quasi-substitutional and paired-Co-doped structures, are considered in our study. Our calculational results indicate that the quasi-substitutional and paired-Co-doped structures can introduce several intermediate bands (IBs) in the band gap and lead to the sub-band gap absorption. The quasi-substitutional and paired-Co-doped structures exhibit red-shift in their sub-band gap absorption spectra when compared to the substitutional structure. The formation energy calculations imply that the material would exhibit thermal stability of absorption in the infrared wavelength.

  12. Local fields in conductor surface electromigration: A first-principles study in the low-bias ballistic limit

    SciTech Connect

    Bevan, Kirk H; Zhu, Wenguang; Stocks, George Malcolm; Guo, Hong; Zhang, Zhenyu

    2012-01-01

    Utilizing first-principles quantum transport calculations, we investigate the role of local fields in conductor surface electromigration. A nanometer-thick Ag(100) thin film is adopted as our prototypical conductor, where we demonstrate the existence of intense local electric fields at atomic surface defects under an external bias. It is shown that such local fields can play an important role in driving surface electromigration and electrical breakdown. The intense fields originate from the relatively short (atomic-scale) screening lengths common to most elemental metals. This general short-range screening trend is established self-consistently within an intuitive picture of linear response electrostatics. The findings shed new light on the underlying physical origins of surface electromigration and point to the possibility of harnessing local fields to engineer electromigration at the nanoscale.

  13. Rapid quantitative pharmacodynamic imaging by a novel method: theory, simulation testing and proof of principle.

    PubMed

    Black, Kevin J; Koller, Jonathan M; Miller, Brad D

    2013-01-01

    Pharmacological challenge imaging has mapped, but rarely quantified, the sensitivity of a biological system to a given drug. We describe a novel method called rapid quantitative pharmacodynamic imaging. This method combines pharmacokinetic-pharmacodynamic modeling, repeated small doses of a challenge drug over a short time scale, and functional imaging to rapidly provide quantitative estimates of drug sensitivity including EC 50 (the concentration of drug that produces half the maximum possible effect). We first test the method with simulated data, assuming a typical sigmoidal dose-response curve and assuming imperfect imaging that includes artifactual baseline signal drift and random error. With these few assumptions, rapid quantitative pharmacodynamic imaging reliably estimates EC 50 from the simulated data, except when noise overwhelms the drug effect or when the effect occurs only at high doses. In preliminary fMRI studies of primate brain using a dopamine agonist, the observed noise level is modest compared with observed drug effects, and a quantitative EC 50 can be obtained from some regional time-signal curves. Taken together, these results suggest that research and clinical applications for rapid quantitative pharmacodynamic imaging are realistic. PMID:23940831

  14. Patch diameter limitation due to high chirp rates in focused SAR images

    NASA Astrophysics Data System (ADS)

    Doerry, Armin W.

    1994-10-01

    Polar-format processed synthetic aperture radar (SAR) images have a limited focused patch diameter that results from unmitigated phase errors. Very high chirp rates, encountered with fine-resolution short-pulse radars, exasperate the problem via a residual video phase error term. This letter modifies the traditional maximum patch diameter expression to include effects of very high chirp rates.

  15. Perfusion Magnetic Resonance Imaging: A Comprehensive Update on Principles and Techniques

    PubMed Central

    Li, Ka-Loh; Ostergaard, Leif; Calamante, Fernando

    2014-01-01

    Perfusion is a fundamental biological function that refers to the delivery of oxygen and nutrients to tissue by means of blood flow. Perfusion MRI is sensitive to microvasculature and has been applied in a wide variety of clinical applications, including the classification of tumors, identification of stroke regions, and characterization of other diseases. Perfusion MRI techniques are classified with or without using an exogenous contrast agent. Bolus methods, with injections of a contrast agent, provide better sensitivity with higher spatial resolution, and are therefore more widely used in clinical applications. However, arterial spin-labeling methods provide a unique opportunity to measure cerebral blood flow without requiring an exogenous contrast agent and have better accuracy for quantification. Importantly, MRI-based perfusion measurements are minimally invasive overall, and do not use any radiation and radioisotopes. In this review, we describe the principles and techniques of perfusion MRI. This review summarizes comprehensive updated knowledge on the physical principles and techniques of perfusion MRI. PMID:25246817

  16. Understanding reliability and some limitations of the images and spectra reconstructed from a multi-monochromatic x-ray imager

    SciTech Connect

    Nagayama, T.; Mancini, R. C.; Mayes, D.; Tommasini, R.; Florido, R.

    2015-11-15

    Temperature and density asymmetry diagnosis is critical to advance inertial confinement fusion (ICF) science. A multi-monochromatic x-ray imager (MMI) is an attractive diagnostic for this purpose. The MMI records the spectral signature from an ICF implosion core with time resolution, 2-D space resolution, and spectral resolution. While narrow-band images and 2-D space-resolved spectra from the MMI data constrain temperature and density spatial structure of the core, the accuracy of the images and spectra depends not only on the quality of the MMI data but also on the reliability of the post-processing tools. Here, we synthetically quantify the accuracy of images and spectra reconstructed from MMI data. Errors in the reconstructed images are less than a few percent when the space-resolution effect is applied to the modeled images. The errors in the reconstructed 2-D space-resolved spectra are also less than a few percent except those for the peripheral regions. Spectra reconstructed for the peripheral regions have slightly but systematically lower intensities by ∼6% due to the instrumental spatial-resolution effects. However, this does not alter the relative line ratios and widths and thus does not affect the temperature and density diagnostics. We also investigate the impact of the pinhole size variation on the extracted images and spectra. A 10% pinhole size variation could introduce spatial bias to the images and spectra of ∼10%. A correction algorithm is developed, and it successfully reduces the errors to a few percent. It is desirable to perform similar synthetic investigations to fully understand the reliability and limitations of each MMI application.

  17. Understanding reliability and some limitations of the images and spectra reconstructed from a multi-monochromatic x-ray imager.

    PubMed

    Nagayama, T; Mancini, R C; Mayes, D; Tommasini, R; Florido, R

    2015-11-01

    Temperature and density asymmetry diagnosis is critical to advance inertial confinement fusion (ICF) science. A multi-monochromatic x-ray imager (MMI) is an attractive diagnostic for this purpose. The MMI records the spectral signature from an ICF implosion core with time resolution, 2-D space resolution, and spectral resolution. While narrow-band images and 2-D space-resolved spectra from the MMI data constrain temperature and density spatial structure of the core, the accuracy of the images and spectra depends not only on the quality of the MMI data but also on the reliability of the post-processing tools. Here, we synthetically quantify the accuracy of images and spectra reconstructed from MMI data. Errors in the reconstructed images are less than a few percent when the space-resolution effect is applied to the modeled images. The errors in the reconstructed 2-D space-resolved spectra are also less than a few percent except those for the peripheral regions. Spectra reconstructed for the peripheral regions have slightly but systematically lower intensities by ∼6% due to the instrumental spatial-resolution effects. However, this does not alter the relative line ratios and widths and thus does not affect the temperature and density diagnostics. We also investigate the impact of the pinhole size variation on the extracted images and spectra. A 10% pinhole size variation could introduce spatial bias to the images and spectra of ∼10%. A correction algorithm is developed, and it successfully reduces the errors to a few percent. It is desirable to perform similar synthetic investigations to fully understand the reliability and limitations of each MMI application. PMID:26628133

  18. Understanding reliability and some limitations of the images and spectra reconstructed from a multi-monochromatic x-ray imager

    NASA Astrophysics Data System (ADS)

    Nagayama, T.; Mancini, R. C.; Mayes, D.; Tommasini, R.; Florido, R.

    2015-11-01

    Temperature and density asymmetry diagnosis is critical to advance inertial confinement fusion (ICF) science. A multi-monochromatic x-ray imager (MMI) is an attractive diagnostic for this purpose. The MMI records the spectral signature from an ICF implosion core with time resolution, 2-D space resolution, and spectral resolution. While narrow-band images and 2-D space-resolved spectra from the MMI data constrain temperature and density spatial structure of the core, the accuracy of the images and spectra depends not only on the quality of the MMI data but also on the reliability of the post-processing tools. Here, we synthetically quantify the accuracy of images and spectra reconstructed from MMI data. Errors in the reconstructed images are less than a few percent when the space-resolution effect is applied to the modeled images. The errors in the reconstructed 2-D space-resolved spectra are also less than a few percent except those for the peripheral regions. Spectra reconstructed for the peripheral regions have slightly but systematically lower intensities by ˜6% due to the instrumental spatial-resolution effects. However, this does not alter the relative line ratios and widths and thus does not affect the temperature and density diagnostics. We also investigate the impact of the pinhole size variation on the extracted images and spectra. A 10% pinhole size variation could introduce spatial bias to the images and spectra of ˜10%. A correction algorithm is developed, and it successfully reduces the errors to a few percent. It is desirable to perform similar synthetic investigations to fully understand the reliability and limitations of each MMI application.

  19. Reaching the Diffraction Limit - Differential Speckle and Wide-Field Imaging for the WIYN Telescope

    NASA Technical Reports Server (NTRS)

    Scott, Nic J.; Howell, Steve; Horch, Elliott

    2016-01-01

    Speckle imaging allows telescopes to achieve diffraction limited imaging performance. The technique requires cameras capable of reading out frames at a very fast rate, effectively 'freezing out' atmospheric seeing. The resulting speckles can be correlated and images reconstructed that are at the diffraction limit of the telescope. These new instruments are based on the successful performance and design of the Differential Speckle Survey Instrument (DSSI).The instruments are being built for the Gemini-N and WIYN telescopes and will be made available to the community via the peer review proposal process. We envision their primary use to be validation and characterization of exoplanet targets from the NASA, K2 and TESS missions and RV discovered exoplanets. Such targets will provide excellent follow-up candidates for both the WIYN and Gemini telescopes. We expect similar data quality in speckle imaging mode with the new instruments. Additionally, both cameras will have a wide-field mode and standard SDSS filters. They will be highly versatile instruments and it is that likely many other science programs will request time on the cameras. The limiting magnitude for speckle observations will remain around 13-14th at WIYN and 16-17th at Gemini, while wide-field, normal CCD imaging operation should be able to go to much fainter, providing usual CCD imaging and photometric capabilities. The instruments will also have high utility as scoring cameras for telescope engineering purposes, or other applications where high time resolution is needed. Instrument support will be provided, including a software pipeline that takes raw speckle data to fully reconstructed images.

  20. Contrast-enhanced harmonic endoscopic ultrasound imaging: Basic principles, present situation and future perspectives

    PubMed Central

    Alvarez-Sánchez, María-Victoria; Napoléon, Bertrand

    2014-01-01

    Over the last decade, the development of stabilised microbubble contrast agents and improvements in available ultrasonic equipment, such as harmonic imaging, have enabled us to display microbubble enhancements on a greyscale with optimal contrast and spatial resolution. Recent technological advances made contrast harmonic technology available for endoscopic ultrasound (EUS) for the first time in 2008. Thus, the evaluation of microcirculation is now feasible with EUS, prompting the evolution of contrast-enhanced EUS from vascular imaging to images of the perfused tissue. Although the relevant experience is still preliminary, several reports have highlighted contrast-enhanced harmonic EUS (CH-EUS) as a promising noninvasive method to visualise and characterise lesions and to differentiate benign from malignant focal lesions. Even if histology remains the gold standard, the combination of CH-EUS and EUS fine needle aspiration (EUS-FNA) can not only render EUS more accurate but may also assist physicians in making decisions when EUS-FNA is inconclusive, increasing the yield of EUS-FNA by guiding the puncture with simultaneous imaging of the vascularity. The development of CH-EUS has also opened up exciting possibilities in other research areas, including monitoring responses to anticancer chemotherapy or to ethanol-induced pancreatic tissue ablation, anticancer therapies based on ultrasound-triggered drug and gene delivery, and therapeutic adjuvants by contrast ultrasound-induced apoptosis. Contrast harmonic imaging is gaining popularity because of its efficacy, simplicity and non-invasive nature, and many expectations are currently resting on this technique. If its potential is confirmed in the near future, contrast harmonic imaging will become a standard practice in EUS. PMID:25400439

  1. Fundamental and practical limitations of FUV/EUV photon-counting image detectors

    NASA Technical Reports Server (NTRS)

    Lampton, M.

    1991-01-01

    In EUV and FUV space-astronomy applications, the best contemporary detector designs are based on the use of microchannel plates due to their ability to deliver photon-counting performance with high efficiency. The major unresolved issue is the choice of position-readout system for the individual photoevents. Electrical event-readout systems are divided into two classes: the discrete wire anodes that perform coordinate digitization by wire-group selection, and the continuous centroid-position encoders for which coordinates are digitized in the associated electronics. The centroid-position encoder techniques are discussed in terms of how they overcome the four chief limitations of the discrete-wire readouts - their limited format size, their flat focal surface, their fundamental hex-channel vs squared-pixel moire pattern, and their image undersampling. With these limitations overcome, microchannel based image systems can deliver the performance demanded by the forthcoming generation of applications in space astronomy.

  2. Applicability, usability, and limitations of murine embryonic imaging with optical coherence tomography and optical projection tomography

    PubMed Central

    Singh, Manmohan; Raghunathan, Raksha; Piazza, Victor; Davis-Loiacono, Anjul M.; Cable, Alex; Vedakkan, Tegy J.; Janecek, Trevor; Frazier, Michael V.; Nair, Achuth; Wu, Chen; Larina, Irina V.; Dickinson, Mary E.; Larin, Kirill V.

    2016-01-01

    We present an analysis of imaging murine embryos at various embryonic developmental stages (embryonic day 9.5, 11.5, and 13.5) by optical coherence tomography (OCT) and optical projection tomography (OPT). We demonstrate that while OCT was capable of rapid high-resolution live 3D imaging, its limited penetration depth prevented visualization of deeper structures, particularly in later stage embryos. In contrast, OPT was able to image the whole embryos, but could not be used in vivo because the embryos must be fixed and cleared. Moreover, the fixation process significantly altered the embryo morphology, which was quantified by the volume of the eye-globes before and after fixation. All of these factors should be weighed when determining which imaging modality one should use to achieve particular goals of a study. PMID:27375945

  3. Limitations and Extensions of the Lock-and-Key Principle: Differences between Gas State, Solution and Solid State Structures

    PubMed Central

    Schneider, Hans-Jörg

    2015-01-01

    The lock-and-key concept is discussed with respect to necessary extensions. Formation of supramolecular complexes depends not only, and often not even primarily on an optimal geometric fit between host and guest. Induced fit and allosteric interactions have long been known as important modifications. Different binding mechanisms, the medium used and pH effects can exert a major influence on the affinity. Stereoelectronic effects due to lone pair orientation can lead to variation of binding constants by orders of magnitude. Hydrophobic interactions due to high-energy water inside cavities modify the mechanical lock-and-key picture. That optimal affinities are observed if the cavity is only partially filled by the ligand can be in conflict with the lock-and-key principle. In crystals other forces than those between host and guest often dominate, leading to differences between solid state and solution structures. This is exemplified in particular with calixarene complexes, which by X-ray analysis more often than other hosts show guest molecules outside their cavity. In view of this the particular problems with the identification of weak interactions in crystals is discussed. PMID:25815592

  4. [Frontiers in Live Bone Imaging Researches. Two-Photon Excitation Microscopy, principles and technologies].

    PubMed

    Oikawa, Yoshiro

    2015-06-01

    The "two photon absorption" phenomenon had been predicted by the American Physicist, Maria Ghöppert-Mayer in 1931. Denk and Webb group had proved it in 1990 and the first product had been launched in the market in 1996. But ever since the product became available, the number of users are not increased. Moreover, the system had been too difficult to use and the system sometimes stay not working in labs. But recently, the new easier-to-use products are released and the ultra short pulse IR laser became stable. And its applications are extending from neuro-science to oncology or immunology fields. Due to these reasons, the shipment of multi-photon microscope in Japan in 2013 is approximately 40 units which is 3 times bigger than in 2010. In this paper, I would like to discuss the principles of two-photon microscopy and some of the new technologies for the higher signal capture efficiency. PMID:26017864

  5. Exploring the limits of ultrafast polymerase chain reaction using liquid for thermal heat exchange: A proof of principle

    NASA Astrophysics Data System (ADS)

    Maltezos, George; Johnston, Matthew; Taganov, Konstantin; Srichantaratsamee, Chutatip; Gorman, John; Baltimore, David; Chantratita, Wasun; Scherer, Axel

    2010-12-01

    Thermal ramp rate is a major limiting factor in using real-time polymerase chain reaction (PCR) for routine diagnostics. We explored the limits of speed by using liquid for thermal exchange rather than metal as in traditional devices, and by testing different polymerases. In a clinical setting, our system equaled or surpassed state-of-the-art devices for accuracy in amplifying DNA/RNA of avian influenza, cytomegalovirus, and human immunodeficiency virus. Using Thermococcus kodakaraensis polymerase and optimizing both electrical and chemical systems, we obtained an accurate, 35 cycle amplification of an 85-base pair fragment of E. coli O157:H7 Shiga toxin gene in as little as 94.1 s, a significant improvement over a typical 1 h PCR amplification.

  6. Capabilities and limitations of neutron imaging for studying soil-root system (Invited)

    NASA Astrophysics Data System (ADS)

    Moradi, A. B.

    2010-12-01

    Soil is heterogeneous by nature. Additional heterogeneity is added to soil as a result of the activities of soil biota and vegetation. Plant roots and soil microorganisms exude organic and inorganic substances into the soil and change the soil properties in their vicinity. They take up water and nutrients and change the distribution of water and ions in the soil. Therefore, most of the soil physical, chemical, and biological parameters in the root-zone have a dynamic character and vary over time and space. Traditional methods of accessing soil parameters such as point-like measurements and extraction of soil solution are for many purposes too invasive, tedious, expensive, and insufficient with respect to spatial and temporal resolution. There is a growing need for the direct, non-destructive and non-invasive measurements of processes such as water flow and solute transport in soils. Imaging techniques provide an opportunity to measure dynamic processes in soil without disturbing the system. Numerous imaging methods have recently been developed and successfully tested in soil and other porous media. However, each method has its own benefits and limitations in applications and often a compromise between real soil conditions and the requirements of each technique is necessary. Neutron imaging is a unique tool to study water dynamics in soil, root developments, and root-soil interactions. This is due to the high interaction probability of hydrogen nuclei with neutrons. Therefore, all proton-bearing materials such as water and roots are easily visualized in great details. For quantitative studies of the processes, however, neutron imaging needs to be combined with proper image analysis techniques. Modeling simulations can also be employed for interpretation of results and for testing our understanding of the system. This study discusses the theory and potential application of neutron imaging as compared with other techniques such as MRI and X-ray. It evaluates the

  7. Limited-memory scaled gradient projection methods for real-time image deconvolution in microscopy

    NASA Astrophysics Data System (ADS)

    Porta, F.; Zanella, R.; Zanghirati, G.; Zanni, L.

    2015-04-01

    Gradient projection methods have given rise to effective tools for image deconvolution in several relevant areas, such as microscopy, medical imaging and astronomy. Due to the large scale of the optimization problems arising in nowadays imaging applications and to the growing request of real-time reconstructions, an interesting challenge to be faced consists in designing new acceleration techniques for the gradient schemes, able to preserve their simplicity and low computational cost of each iteration. In this work we propose an acceleration strategy for a state-of-the-art scaled gradient projection method for image deconvolution in microscopy. The acceleration idea is derived by adapting a step-length selection rule, recently introduced for limited-memory steepest descent methods in unconstrained optimization, to the special constrained optimization framework arising in image reconstruction. We describe how important issues related to the generalization of the step-length rule to the imaging optimization problem have been faced and we evaluate the improvements due to the acceleration strategy by numerical experiments on large-scale image deconvolution problems.

  8. Overcoming the diffraction limit of imaging nanoplasmonic arrays by microspheres and microfibers.

    PubMed

    Allen, Kenneth W; Farahi, Navid; Li, Yangcheng; Limberopoulos, Nicholaos I; Walker, Dennis E; Urbas, Augustine M; Astratov, Vasily N

    2015-09-21

    Super-resolution microscopy by microspheres emerged as a simple and broadband imaging technique; however, the mechanisms of imaging are debated in the literature. Furthermore, the resolution values were estimated based on semi-quantitative criteria. The primary goals of this work are threefold: i) to quantify the spatial resolution provided by this method, ii) to compare the resolution of nanoplasmonic structures formed by different metals, and iii) to understand the imaging provided by microfibers. To this end, arrays of Au and Al nanoplasmonic dimers with very similar geometry were imaged using confocal laser scanning microscopy at λ = 405 nm through high-index (n~1.9-2.2) liquid-immersed BaTiO3 microspheres and through etched silica microfibers. We developed a treatment of super-resolved images in label-free microscopy based on using point-spread functions with subdiffraction-limited widths. It is applicable to objects with arbitrary shapes and can be viewed as an integral form of the super-resolution quantification widely accepted in fluorescent microscopy. In the case of imaging through microspheres, the resolution ~λ/6-λ/7 is demonstrated for Au and Al nanoplasmonic arrays. In the case of imaging through microfibers, the resolution ~λ/6 with magnification M~2.1 is demonstrated in the direction perpendicular to the fiber with hundreds of times larger field-of-view in comparison to microspheres. PMID:26406653

  9. First-principles thermoelasticity of transition metals at high pressure I. Tantalum prototype in the quasi-harmonic limit

    SciTech Connect

    Orlikowski, D; Soderlind, P; Moriarty, J A

    2006-04-25

    The thermoelastic properties of bcc tantalum have been investigated over a broad range of pressures (up to 10 Mbar) and temperatures (up to 26,000 K) using a new first-principles approach that accurately accounts for cold, electron-thermal, and ion-thermal contributions in materials where anharmonic effects are small. Specifically, we have combined ab initio full-potential linear-muffin-tin-orbital (FP-LMTO) electronic-structure calculations for the cold and electron-thermal contributions to the elastic moduli with phonon contributions for the ion-thermal part calculated using model generalized pseudopotential theory (MGPT). For the latter, a summation of terms over the Brillouin zone is performed within the quasi-harmonic approximation, where each term is composed of a strain derivative of the phonon frequency at a particular k point. At ambient pressure, the resulting temperature dependence of the Ta elastic moduli is in excellent agreement with ultrasonic measurements. The experimentally observed anomalous behavior of C{sub 44} at low temperatures is shown to originate from the electron-thermal contribution. At higher temperatures, the main contribution to the temperature dependence of the elastic moduli comes from thermal expansion, but inclusion of the electron- and ion-thermal contributions is essential to obtain quantitative agreement with experiment. In addition, the pressure dependence of the moduli at ambient temperature compares well with recent diamond-anvil cell measurements to 1.05 Mbar. Moreover, the calculated longitudinal and bulk sound velocities in polycrystalline Ta at higher pressure and temperature in the vicinity of shock melting ({approx} 3 Mbar) agree well with data obtained from shock experiments. However, at high temperatures along the melt curve above 1 Mbar, the B{prime} shear modulus becomes negative indicating the onset of unexpectedly strong anharmonic effects. Finally, the assumed temperature dependence of the Steinberg

  10. FRIDA, the diffraction limited NIR imager and IFS for the GTC

    NASA Astrophysics Data System (ADS)

    López, J. A.; Acosta, J.; Álvarez, L. C.; Bringas, V.; Cardiel, N.; Clark, D. M.; Corrales, A.; Cuevas, S.; Chapa, O.; Díaz, J. J., Eikenberry, S. S.; Eliche, C.; Espejo, C.; Flores, R.; Fuentes, J.; Gallego, J.; Garcés, L.; Garzón, F.; Hammersley, P.; Keiman, C.; Lara, G.; López, P.; Lucero, D.; Moreno, H.; Pascual, S.; Patrón, J.; Prieto, A.; Rodríguez, A.; Rodríguez, B.; Sánchez, B.; Torres, D.; Uribe, J.; Watson, A.

    2015-05-01

    FRIDA (InFRared Imager and Dissector for the Adaptive optics system of GTC) is a near infrared, diffraction limited imager and integral field spectrograph that has been designed and is being built as a collaborative project between GTC partner institutions from México, Spain and the USA. FRIDA will operate with the adaptive optics system of GTC. Three different scales are provided in imaging mode, 0.010, 0.020 and 0.040 arcsec pixel^{-1}. The integral field unit is based on a monolithic image slicer that will slice up the field of view into 30 slices. The IFS spaxels have a 2:1 pixels aspect ratio (2 along the spectral axis an 1 along the spatial axis) and it will offer three different spectral resolutions, R ˜ 1000, 5000 and 30,000, the latter over selectable regions in the H & K bands. Thus FRIDA will exploit the diffraction limit of a 10.4 m telescope with superb image quality and spectral resolutions suitable to tackle a large range of topical astrophysical problems. FRIDA has started systems integration and is scheduled to be ready for fully integrated system tests by the end of 2015 and be delivered to GTC shortly after. Here we present an overview of its design, current status and potential scientific applications.

  11. Whole slide imaging: uses and limitations for surgical pathology and teaching.

    PubMed

    Boyce, B F

    2015-07-01

    Advances in computer and software technology and in the quality of images produced by digital cameras together with development of robotic devices that can take glass histology slides from a cassette holding many slides and place them in a conventional microscope for electronic scanning have facilitated the development of whole slide imaging (WSI) systems during the past decade. Anatomic pathologists now have opportunities to test the utility of WSI systems for diagnostic, teaching and research purposes and to determine their limitations. Uses include rendering primary diagnoses from scanned hematoxylin and eosin stained tissues on slides, reviewing frozen section or routine slides from remote locations for interpretation or consultation. Also, WSI can replace physical storage of glass slides with digital images, storing images of slides from outside institutions, presenting slides at clinical or research conferences, teaching residents and medical students, and storing fluorescence images without fading or quenching of the fluorescence signal. Limitations include the high costs of the scanners, maintenance contracts and IT support, storage of digital files and pathologists' lack of familiarity with the technology. Costs are falling as more devices and systems are sold and cloud storage costs drop. Pathologist familiarity with the technology will grow as more institutions purchase WSI systems. The technology holds great promise for the future of anatomic pathology. PMID:25901738

  12. Limitations in Determining Multifractal Spectra from Pore-Solid Soil Aggregate Images

    SciTech Connect

    Kravchenko, A N; Martin, M A; Smucker, A J.M.; Rivers, M L

    2011-11-16

    Multifractal methods have the potential to be useful tools for characterizing spatial distributions of soil pores from microtomographic images of undisturbed soil cores and soil aggregates. The objective of this study was to examine the limitations of multifractal analyses in binary (void and solid) soil images and to explore conditions under which multifractal spectra can be obtained. Multifractal characteristics of binary soil images are bounded within certain limiting values corresponding to nonfractal scaling. In this study, we first addressed the theoretical limitations of multifractal analysis of binary images and examined the nonfractal scaling boundaries in multifractal calculations by the method of moments. Then we developed boundary conditions for multifractal calculations by the direct method. Results revealed that fractal scaling is potentially possible only across a relatively narrow range of cell sizes restricted by the nonfractal scaling boundaries. Moreover, the range of cell sizes where fractal scaling is potentially possible varies with pore size. That is, in multifractal calculations it changes continuously with changes in the q value. For the soil aggregates examined in this study, this range varied from two to eight pixels for low q values to 128 pixels for high q values. The varying range makes calculations of true multifractal spectra for binary soil image data impossible. These results are consistent with a general theoretical notion that binary soil images are not multifractal in a strict mathematical sense. We suggest, however, that application of multifractal formalism can generate 'pseudo-multifractal spectra' that might still be useful for summarizing pore distribution information and for comparing pore data among different agricultural management regimes and soil type.

  13. An Image Reconstruction Algorithm for Electrical Capacitance Tomography Based on Robust Principle Component Analysis

    PubMed Central

    Lei, Jing; Liu, Shi; Wang, Xueyao; Liu, Qibin

    2013-01-01

    Electrical capacitance tomography (ECT) attempts to reconstruct the permittivity distribution of the cross-section of measurement objects from the capacitance measurement data, in which reconstruction algorithms play a crucial role in real applications. Based on the robust principal component analysis (RPCA) method, a dynamic reconstruction model that utilizes the multiple measurement vectors is presented in this paper, in which the evolution process of a dynamic object is considered as a sequence of images with different temporal sparse deviations from a common background. An objective functional that simultaneously considers the temporal constraint and the spatial constraint is proposed, where the images are reconstructed by a batching pattern. An iteration scheme that integrates the advantages of the alternating direction iteration optimization (ADIO) method and the forward-backward splitting (FBS) technique is developed for solving the proposed objective functional. Numerical simulations are implemented to validate the feasibility of the proposed algorithm. PMID:23385418

  14. Limited-angle tomography for analyzer-based phase-contrast x-ray imaging

    NASA Astrophysics Data System (ADS)

    Majidi, Keivan; Wernick, Miles N.; Li, Jun; Muehleman, Carol; Brankov, Jovan G.

    2014-07-01

    Multiple-image radiography (MIR) is an analyzer-based phase-contrast x-ray imaging method, which is emerging as a potential alternative to conventional radiography. MIR simultaneously generates three planar parametric images containing information about scattering, refraction and attenuation properties of the object. The MIR planar images are linear tomographic projections of the corresponding object properties, which allows reconstruction of volumetric images using computed tomography (CT) methods. However, when acquiring a full range of linear projections around the tissue of interest is not feasible or the scanning time is limited, limited-angle tomography techniques can be used to reconstruct these volumetric images near the central plane, which is the plane that contains the pivot point of the tomographic movement. In this work, we use computer simulations to explore the applicability of limited-angle tomography to MIR. We also investigate the accuracy of reconstructions as a function of number of tomographic angles for a fixed total radiation exposure. We use this function to find an optimal range of angles over which data should be acquired for limited-angle tomography MIR (LAT-MIR). Next, we apply the LAT-MIR technique to experimentally acquired MIR projections obtained in a cadaveric human thumb study. We compare the reconstructed slices near the central plane to the same slices reconstructed by CT-MIR using the full angular view around the object. Finally, we perform a task-based evaluation of LAT-MIR performance for different numbers of angular views, and use template matching to detect cartilage in the refraction image near the central plane. We use the signal-to-noise ratio of this test as the detectability metric to investigate an optimum range of tomographic angles for detecting soft tissues in LAT-MIR. Both results show that there is an optimum range of angular view for data acquisition where LAT-MIR yields the best performance, comparable to CT

  15. Limited-angle tomography for analyzer-based phase-contrast X-ray imaging

    PubMed Central

    Majidi, Keivan; Wernick, Miles N; Li, Jun; Muehleman, Carol; Brankov, Jovan G

    2014-01-01

    Multiple-Image Radiography (MIR) is an analyzer-based phase-contrast X-ray imaging method (ABI), which is emerging as a potential alternative to conventional radiography. MIR simultaneously generates three planar parametric images containing information about scattering, refraction and attenuation properties of the object. The MIR planar images are linear tomographic projections of the corresponding object properties, which allows reconstruction of volumetric images using computed tomography (CT) methods. However, when acquiring a full range of linear projections around the tissue of interest is not feasible or the scanning time is limited, limited-angle tomography techniques can be used to reconstruct these volumetric images near the central plane, which is the plane that contains the pivot point of the tomographic movement. In this work, we use computer simulations to explore the applicability of limited-angle tomography to MIR. We also investigate the accuracy of reconstructions as a function of number of tomographic angles for a fixed total radiation exposure. We use this function to find an optimal range of angles over which data should be acquired for limited-angle tomography MIR (LAT-MIR). Next, we apply the LAT-MIR technique to experimentally acquired MIR projections obtained in a cadaveric human thumb study. We compare the reconstructed slices near the central plane to the same slices reconstructed by CT-MIR using the full angular view around the object. Finally, we perform a task-based evaluation of LAT-MIR performance for different numbers of angular views, and use template matching to detect cartilage in the refraction image near the central plane. We use the signal-to-noise ratio of this test as the detectability metric to investigate an optimum range of tomographic angles for detecting soft tissues in LAT-MIR. Both results show that there is an optimum range of angular view for data acquisition where LAT-MIR yields the best performance, comparable to

  16. A limited-memory, quasi-Newton preconditioner for nonnegatively constrained image reconstruction.

    PubMed

    Bardsley, Johnathan M

    2004-05-01

    Image reconstruction gives rise to some challenging large-scale constrained optimization problems. We consider a convex minimization problem with nonnegativity constraints that arises in astronomical imaging. To solve this problem, we use an efficient hybrid gradient projection-reduced Newton (active-set) method. By "reduced Newton," we mean that we take Newton steps only in the inactive variables. Owing to the large size of our problem, we compute approximate reduced Newton steps by using the conjugate gradient (CG) iteration. We introduce a limited-memory, quasi-Newton preconditioner that speeds up CG convergence. A numerical comparison is presented that demonstrates the effectiveness of this preconditioner. PMID:15139424

  17. Operating principles and detection characteristics of the Visible and Near-Infrared Imaging Spectrometer in the Chang'e-3

    NASA Astrophysics Data System (ADS)

    He, Zhi-Ping; Wang, Bin-Yong; Lü, Gang; Li, Chun-Lai; Yuan, Li-Yin; Xu, Rui; Liu, Bin; Chen, Kai; Wang, Jian-Yu

    2014-12-01

    The Visible and Near-Infrared Imaging Spectrometer (VNIS), using two acousto-optic tunable filters as dispersive components, consists of a VIS/NIR imaging spectrometer (0.45-0.95 μm), a shortwave IR spectrometer (0.9-2.4 μm) and a calibration unit with dust-proofing functionality. The VNIS was utilized to detect the spectrum of the lunar surface and achieve in-orbit calibration, which satisfied the requirements for scientific detection. Mounted at the front of the Yutu rover, lunar objects that are detected with the VNIS with a 45° visual angle to obtain spectra and geometrical data in order to analyze the mineral composition of the lunar surface. After landing successfully on the Moon, the VNIS performed several explorations and calibrations, and obtained several spectral images and spectral reflectance curves of the lunar soil in the region of Mare Imbrium. This paper describes the working principle and detection characteristics of the VNIS and provides a reference for data processing and scientific applications.

  18. A Bayesian approach to distinguishing interdigitated tongue muscles from limited diffusion magnetic resonance imaging.

    PubMed

    Ye, Chuyang; Murano, Emi; Stone, Maureen; Prince, Jerry L

    2015-10-01

    The tongue is a critical organ for a variety of functions, including swallowing, respiration, and speech. It contains intrinsic and extrinsic muscles that play an important role in changing its shape and position. Diffusion tensor imaging (DTI) has been used to reconstruct tongue muscle fiber tracts. However, previous studies have been unable to reconstruct the crossing fibers that occur where the tongue muscles interdigitate, which is a large percentage of the tongue volume. To resolve crossing fibers, multi-tensor models on DTI and more advanced imaging modalities, such as high angular resolution diffusion imaging (HARDI) and diffusion spectrum imaging (DSI), have been proposed. However, because of the involuntary nature of swallowing, there is insufficient time to acquire a sufficient number of diffusion gradient directions to resolve crossing fibers while the in vivo tongue is in a fixed position. In this work, we address the challenge of distinguishing interdigitated tongue muscles from limited diffusion magnetic resonance imaging by using a multi-tensor model with a fixed tensor basis and incorporating prior directional knowledge. The prior directional knowledge provides information on likely fiber directions at each voxel, and is computed with anatomical knowledge of tongue muscles. The fiber directions are estimated within a maximum a posteriori (MAP) framework, and the resulting objective function is solved using a noise-aware weighted ℓ1-norm minimization algorithm. Experiments were performed on a digital crossing phantom and in vivo tongue diffusion data including three control subjects and four patients with glossectomies. On the digital phantom, effects of parameters, noise, and prior direction accuracy were studied, and parameter settings for real data were determined. The results on the in vivo data demonstrate that the proposed method is able to resolve interdigitated tongue muscles with limited gradient directions. The distributions of the

  19. Designing and Interpreting Limiting Dilution Assays: General Principles and Applications to the Latent Reservoir for Human Immunodeficiency Virus-1

    PubMed Central

    Rosenbloom, Daniel I. S.; Elliott, Oliver; Hill, Alison L.; Henrich, Timothy J.; Siliciano, Janet M.; Siliciano, Robert F.

    2015-01-01

    Limiting dilution assays are widely used in infectious disease research. These assays are crucial for current human immunodeficiency virus (HIV)-1 cure research in particular. In this study, we offer new tools to help investigators design and analyze dilution assays based on their specific research needs. Limiting dilution assays are commonly used to measure the extent of infection, and in the context of HIV they represent an essential tool for studying latency and potential curative strategies. Yet standard assay designs may not discern whether an intervention reduces an already miniscule latent infection. This review addresses challenges arising in this setting and in the general use of dilution assays. We illustrate the major statistical method for estimating frequency of infectious units from assay results, and we offer an online tool for computing this estimate. We recommend a procedure for customizing assay design to achieve desired sensitivity and precision goals, subject to experimental constraints. We consider experiments in which no viral outgrowth is observed and explain how using alternatives to viral outgrowth may make measurement of HIV latency more efficient. Finally, we discuss how biological complications, such as probabilistic growth of small infections, alter interpretations of experimental results. PMID:26478893

  20. Designing and Interpreting Limiting Dilution Assays: General Principles and Applications to the Latent Reservoir for Human Immunodeficiency Virus-1.

    PubMed

    Rosenbloom, Daniel I S; Elliott, Oliver; Hill, Alison L; Henrich, Timothy J; Siliciano, Janet M; Siliciano, Robert F

    2015-12-01

    Limiting dilution assays are widely used in infectious disease research. These assays are crucial for current human immunodeficiency virus (HIV)-1 cure research in particular. In this study, we offer new tools to help investigators design and analyze dilution assays based on their specific research needs. Limiting dilution assays are commonly used to measure the extent of infection, and in the context of HIV they represent an essential tool for studying latency and potential curative strategies. Yet standard assay designs may not discern whether an intervention reduces an already miniscule latent infection. This review addresses challenges arising in this setting and in the general use of dilution assays. We illustrate the major statistical method for estimating frequency of infectious units from assay results, and we offer an online tool for computing this estimate. We recommend a procedure for customizing assay design to achieve desired sensitivity and precision goals, subject to experimental constraints. We consider experiments in which no viral outgrowth is observed and explain how using alternatives to viral outgrowth may make measurement of HIV latency more efficient. Finally, we discuss how biological complications, such as probabilistic growth of small infections, alter interpretations of experimental results. PMID:26478893

  1. [Magnetic resonance image fusion based on three dimensional band limited shearlet transform].

    PubMed

    Duan, Chang; Wang, Xuegang; Wang, Hong; Wang, Shuai

    2015-02-01

    More and more medical devices can capture different features of human body and form three dimensional (3D) images. In clinical applications, usually it is required to fuse multiple source images containing different and crucial information into one for the purpose of assisting medical treatment. However, traditional image fusion methods are normally designed for two dimensional (2D) images and will lead to loss of the third dimensional information if directly applied to 3D data. Therefore, a novel 3D magnetic image fusion method was proposed based on the combination of newly invented beyond wavelet transform, called 3D band limited shearlet transformand (BLST), and four groups of traditional fusion rules. The proposed method was then compared with the 2D and 3D wavelet and dual-tree complex wavelet transform fusion methods through 4 groups of human brain T2* and quantitative susceptibility mapping (QSM) images. The experiments indicated that the performance of the method based on 3D transform was generally superior to the existing methods based on 2D transform. Taking advantage of direction representation, shearlet transform could effectively improve the performance of conventional fusion method based on 3D transform. It is well concluded, therefore, that the proposed method is the best among the methods based on 2D and 3D transforms. PMID:25997289

  2. Regularising limited view tomography using anatomical reference images and information theoretic similarity metrics.

    PubMed

    Van de Sompel, Dominique; Brady, Michael

    2012-01-01

    This paper is concerned with limited view tomography. Inspired by the application of digital breast tomosynthesis (DBT), which is but one of an increasing number of applications of limited view tomography, we concentrate primarily on cases where the angular range is restricted to a narrow wedge of approximately ±30°, and the number of views is restricted to 10-30. The main challenge posed by these conditions is undersampling, also known as the null space problem. As a consequence of the Fourier Slice Theorem, a limited angular range leaves large swathes of the object's Fourier space unsampled, leaving a large space of possible solutions, reconstructed volumes, for a given set of inputs. We explore the feasibility of using same- or different-modality images as anatomical priors to constrain the null space, hence the solution. To allow for different-modality priors, we choose information theoretic measures to quantify the similarity between reconstructions and their priors. We demonstrate the limitations of two popular choices, namely mutual information and joint entropy, and propose robust alternatives that overcome their limitations. One of these alternatives is essentially a joint mixture model of the image and its prior. Promising mitigation of the data insufficiency problem is demonstrated using 2D synthetic as well as clinical phantoms. This work initially assumes a priori registered priors, and is then extended to allow for the registration to be performed simultaneously with the reconstruction. PMID:21962917

  3. Overcoming the resolution limit in retinal imaging using the scattering properties of the sclera (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Carpentras, Dino; Laforest, Timothé; Psaltis, Demetri; Moser, Christophe

    2016-03-01

    In-vivo imaging of the eye's fundus is widely used to study eye's health. State of the art Adaptive Optics devices can resolve features up to a lateral resolution of 1.5 um. This resolution is still above what is needed to observe sub-cellular structures such as cone cells (1-1.25 um diameter). This limit in resolution is due to the small numerical aperture of the eye when the pupil is fully dilated (max 0.24). In our work, we overcome this limit using a non-standard illumination scheme. A laser beam is shined on the lateral choroid layer, whose scattered light is illuminating the eye's fundus. Thanks to a Spatial Light Modulator the scattered light from the choroid layer can be manipulated to produce a scanning focus spot on the fundus. The intensity of the reflected light from the fundus is collected from the pupil and used for reconstructing the image.

  4. Planoconcave optical microresonator sensors for photoacoustic imaging: pushing the limits of sensitivity (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Guggenheim, James A.; Zhang, Edward Z.; Beard, Paul C.

    2016-03-01

    Most photoacoustic scanners use piezoelectric detectors but these have two key limitations. Firstly, they are optically opaque, inhibiting backward mode operation. Secondly, it is difficult to achieve adequate detection sensitivity with the small element sizes needed to provide near-omnidirectional response as required for tomographic imaging. Planar Fabry-Perot (FP) ultrasound sensing etalons can overcome both of these limitations and have proved extremely effective for superficial (<1cm) imaging applications. To achieve small element sizes (<100μm), the etalon is illuminated with a focused laser beam. However, this has the disadvantage that beam walk-off due to the divergence of the beam fundamentally limits the etalon finesse and thus sensitivity - in essence, the problem is one of insufficient optical confinement. To overcome this, novel planoconcave micro-resonator sensors have been fabricated using precision ink-jet printed polymer domes with curvatures matching that of the laser wavefront. By providing near-perfect beam confinement, we show that it is possible to approach the maximum theoretical limit for finesse (f) imposed by the etalon mirror reflectivities (e.g. f=400 for R=99.2% in contrast to a typical planar sensor value of f<50). This yields an order of magnitude increase in sensitivity over a planar FP sensor with the same acoustic bandwidth. Furthermore by eliminating beam walk-off, viable sensors can be made with significantly greater thickness than planar FP sensors. This provides an additional sensitivity gain for deep tissue imaging applications such as breast imaging where detection bandwidths in the low MHz can be tolerated. For example, for a 250 μm thick planoconcave sensor with a -3dB bandwidth of 5MHz, the measured NEP was 4 Pa. This NEP is comparable to that provided by mm scale piezoelectric detectors used for breast imaging applications but with more uniform frequency response characteristics and an order-of-magnitude smaller element

  5. Long-baseline optical intensity interferometry. Laboratory demonstration of diffraction-limited imaging

    NASA Astrophysics Data System (ADS)

    Dravins, Dainis; Lagadec, Tiphaine; Nuñez, Paul D.

    2015-08-01

    Context. A long-held vision has been to realize diffraction-limited optical aperture synthesis over kilometer baselines. This will enable imaging of stellar surfaces and their environments, and reveal interacting gas flows in binary systems. An opportunity is now opening up with the large telescope arrays primarily erected for measuring Cherenkov light in air induced by gamma rays. With suitable software, such telescopes could be electronically connected and also used for intensity interferometry. Second-order spatial coherence of light is obtained by cross correlating intensity fluctuations measured in different pairs of telescopes. With no optical links between them, the error budget is set by the electronic time resolution of a few nanoseconds. Corresponding light-travel distances are approximately one meter, making the method practically immune to atmospheric turbulence or optical imperfections, permitting both very long baselines and observing at short optical wavelengths. Aims: Previous theoretical modeling has shown that full images should be possible to retrieve from observations with such telescope arrays. This project aims at verifying diffraction-limited imaging experimentally with groups of detached and independent optical telescopes. Methods: In a large optics laboratory, artificial stars (single and double, round and elliptic) were observed by an array of small telescopes. Using high-speed photon-counting solid-state detectors and real-time electronics, intensity fluctuations were cross-correlated over up to 180 baselines between pairs of telescopes, producing coherence maps across the interferometric Fourier-transform plane. Results: These interferometric measurements were used to extract parameters about the simulated stars, and to reconstruct their two-dimensional images. As far as we are aware, these are the first diffraction-limited images obtained from an optical array only linked by electronic software, with no optical connections between the

  6. Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging.

    PubMed

    Khorasaninejad, Mohammadreza; Chen, Wei Ting; Devlin, Robert C; Oh, Jaewon; Zhu, Alexander Y; Capasso, Federico

    2016-06-01

    Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy. PMID:27257251

  7. Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging

    NASA Astrophysics Data System (ADS)

    Khorasaninejad, Mohammadreza; Chen, Wei Ting; Devlin, Robert C.; Oh, Jaewon; Zhu, Alexander Y.; Capasso, Federico

    2016-06-01

    Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.

  8. Compressed ultrafast photography (CUP): redefining the limit of passive ultrafast imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Gao, Liang S.

    2016-03-01

    Video recording of ultrafast phenomena using a detector array based on the CCD or CMOS technologies is fundamentally limited by the sensor's on-chip storage and data transfer speed. To get around this problem, the most practical approach is to utilize a streak camera. However, the resultant image is normally one dimensional—only a line of the scene can be seen at a time. Acquiring a two-dimensional image thus requires mechanical scanning across the entire field of view. This requirement poses severe restrictions on the applicable scenes because the event itself must be repetitive. To overcome these limitations, we have developed a new computational ultrafast imaging method, referred to as compressed ultrafast photography (CUP), which can capture two-dimensional dynamic scenes at up to 100 billion frames per second. Based on the concept of compressed sensing, CUP works by encoding the input scene with a random binary pattern in the spatial domain, followed by shearing the resultant image in a streak camera with a fully-opened entrance slit. The image reconstruction is the solution of the inverse problem of above processes. Given sparsity in the spatiotemporal domain, the original event datacube can be reasonably estimated by employing a two-step iterative shrinkage/thresholding algorithm. To demonstrate CUP, we imaged light reflection, refraction, and racing in two different media (air and resin). Our technique, for the first time, enables video recording of photon propagation at a temporal resolution down to tens of picoseconds. Moreover, to further expand CUP's functionality, we added a color separation unit to the system, thereby allowing simultaneous acquisition of a four-dimensional datacube (x,y,t,λ), where λ is wavelength, within a single camera snapshot.

  9. Simulation in infrared imaging: Using electrical circuit principles to model heat transfer

    NASA Astrophysics Data System (ADS)

    Evans, Ronald J.

    1992-01-01

    Simulation of thermal or infrared imaging involves modeling the heat exchange between database features and external sources of heat or radiation (e.g., the sun). One approach to computing differential scene irradiance, as viewed by a sensor, employs electrical circuit theory to model heat transfer between the database objects within the scene. In this report, practical shortcomings of this circuit approach and possible alternatives are introduced and analyzed. Heat storage (capacitance) was one process simulated. Results showed that the computational changes required to implement thermal capacitance are difficult to simulate numerically. Individual feature estimates of capacity were inconsistent with expectations. In addition, the temperature contribution from the capacity or time-varying component did not overcome the effect of the steady-state component, which contained a significant amount of error from assumptions made in the circuit model. Further work is required to identify approaches which provide less extreme object temperatures throughout a diurnal or daily cycle.

  10. Simulation in infrared imaging - Using electrical circuit principles to model heat transfer

    NASA Astrophysics Data System (ADS)

    Evans, R. J.

    Simulation of thermal or infrared imaging involves modeling the heat exchange between database features and external sources of heat or radiation (e.g., the sun). One approach to computing differential scene irradiance, as viewed by a sensor, employs electrical circuit theory to model heat transfer between the database objects within the scene. In this report, practical shortcomings of this circuit approach and possible alternatives are introduced and analyzed. Heat storage (capacitance) was one process simulated. Results showed that the computational changesa reqauired to implement thermal capacitance are difficult to simulate numerically. Individual feature estimates of capacity were inconsistent with expectations. In addition, the temperature condtribution from the capacity or time-varyhing component did not overcome the effect of the steady-state component, which contained a significant amount of error from assumptions made in the circuit model. Further work is required to identyify approaches which provide less extreme object temperaturtes throughout a diurnal or daily cycle.

  11. Feature Visibility Limits in the Non-Linear Enhancement of Turbid Images

    NASA Technical Reports Server (NTRS)

    Jobson, Daniel J.; Rahman, Zia-ur; Woodell, Glenn A.

    2003-01-01

    The advancement of non-linear processing methods for generic automatic clarification of turbid imagery has led us from extensions of entirely passive multiscale Retinex processing to a new framework of active measurement and control of the enhancement process called the Visual Servo. In the process of testing this new non-linear computational scheme, we have identified that feature visibility limits in the post-enhancement image now simplify to a single signal-to-noise figure of merit: a feature is visible if the feature-background signal difference is greater than the RMS noise level. In other words, a signal-to-noise limit of approximately unity constitutes a lower limit on feature visibility.

  12. Strengths and Limitations of Current Adult Nomograms for the Aorta Obtained by Noninvasive Cardiovascular Imaging.

    PubMed

    Cantinotti, Massimiliano; Giordano, Raffaele; Clemente, Alberto; Assanta, Nadia; Murzi, Michele; Murzi, Bruno; Crocetti, Maura; Marotta, Marco; Scalese, Marco; Kutty, Shelby; Iervasi, Giorgio

    2016-07-01

    Normalized measurements for the evaluation of aortic disease severity are preferred to the adoption of generic cutoff values. The purpose of this review is to evaluate the strengths and limitations of currently available aortic nomograms by echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI). A literature search was conducted accessing the National Library of Medicine using the keywords normal values, aorta, echocardiography, CT, and MRI. Addition of these keywords further refined the results: reference values, nomograms, aortic arch, and adults. Thirty studies were included in the final analysis. Despite the strengths noted in the recent investigations, multiple methodological and numerical limitations emerged. The numerical limitations included sample size limitation in most of the studies (only few investigations consisted of >800 subjects and many had 70-300), lack of aortic arch measurements, and paucity of data for non-Caucasian subjects. Methodological limitations consisted of lack of standardization in measurements (systole vs. diastole, internal vs. external border, axial vs. orthogonal planes), heterogeneity and data normalization issues (various age intervals used, body size often not evaluated, data expressed as observed values rather than estimated values by z-score), and study design issues. The designs were mostly retrospective with poorly defined inclusion and exclusion criteria. The nomograms presented range of normality with significant differences, but also with some reproducible pattern. Despite recent advances, multiple methodological or numerical limitations exist in adult nomograms for the aorta. Comprehensive nomograms of aortic dimensions at multiple levels including the aortic arch for different imaging techniques, involving a wide sample size, and using standardized methodology for measurements and data normalization are warranted. The availability of robust nomograms may encourage the use of personalized

  13. First results from IRENI - Rapid diffraction-limited high resolution imaging across the mid-infrared bandwidth

    SciTech Connect

    Nasse, Michael J.; Mattson, Eric; Hirschmugl, Carol

    2010-02-03

    First results from IRENI, a new beamline at the Synchrotron Radiation Center, demonstrate that synchrotron chemical imaging, which combines the characteristics of bright, stable, broadband synchrotron source with a multi-element detector, produces diffraction-limited images at all wavelengths simultaneously. A single cell of Micrasterias maintained in a flow cell has been measured, and results show high quality spectra and images demonstrating diffraction limited, and therefore wavelength-dependent, spatial resolution.

  14. Fundamental Limitations of High Contrast Imaging Set by Small Sample Statistics

    NASA Astrophysics Data System (ADS)

    Mawet, D.; Milli, J.; Wahhaj, Z.; Pelat, D.; Absil, O.; Delacroix, C.; Boccaletti, A.; Kasper, M.; Kenworthy, M.; Marois, C.; Mennesson, B.; Pueyo, L.

    2014-09-01

    In this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star, the number of resolution elements decreases rapidly toward small angles. This reduction of the number of degrees of freedom dramatically affects CLs and false alarm probabilities. Naively using the same ideal hypothesis and methods as for larger separations, which are well understood and commonly assume Gaussian noise, can yield up to one order of magnitude error in contrast estimations at fixed CL. The statistical penalty exponentially increases toward very small inner working angles. Even at 5-10 resolution elements from the star, false alarm probabilities can be significantly higher than expected. Here we present a rigorous statistical analysis that ensures robustness of the CL, but also imposes a substantial limitation on corresponding achievable detection limits (thus contrast) at small angles. This unavoidable fundamental statistical effect has a significant impact on current coronagraphic and future high-contrast imagers. Finally, the paper concludes with practical recommendations to account for small number statistics when computing the sensitivity to companions at small angles and when exploiting the results of direct imaging planet surveys.

  15. Fundamental limitations of high contrast imaging set by small sample statistics

    SciTech Connect

    Mawet, D.; Milli, J.; Wahhaj, Z.; Pelat, D.; Absil, O.; Delacroix, C.; Boccaletti, A.; Kasper, M.; Kenworthy, M.; Marois, C.; Mennesson, B.; Pueyo, L.

    2014-09-10

    In this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star, the number of resolution elements decreases rapidly toward small angles. This reduction of the number of degrees of freedom dramatically affects CLs and false alarm probabilities. Naively using the same ideal hypothesis and methods as for larger separations, which are well understood and commonly assume Gaussian noise, can yield up to one order of magnitude error in contrast estimations at fixed CL. The statistical penalty exponentially increases toward very small inner working angles. Even at 5-10 resolution elements from the star, false alarm probabilities can be significantly higher than expected. Here we present a rigorous statistical analysis that ensures robustness of the CL, but also imposes a substantial limitation on corresponding achievable detection limits (thus contrast) at small angles. This unavoidable fundamental statistical effect has a significant impact on current coronagraphic and future high-contrast imagers. Finally, the paper concludes with practical recommendations to account for small number statistics when computing the sensitivity to companions at small angles and when exploiting the results of direct imaging planet surveys.

  16. Digital image processing.

    PubMed

    Seeram, Euclid

    2004-01-01

    Digital image processing is now commonplace in radiology, nuclear medicine and sonography. This article outlines underlying principles and concepts of digital image processing. After completing this article, readers should be able to: List the limitations of film-based imaging. Identify major components of a digital imaging system. Describe the history and application areas of digital image processing. Discuss image representation and the fundamentals of digital image processing. Outline digital image processing techniques and processing operations used in selected imaging modalities. Explain the basic concepts and visualization tools used in 3-D and virtual reality imaging. Recognize medical imaging informatics as a new area of specialization for radiologic technologists. PMID:15352557

  17. Quantitative nanoscopy: Tackling sampling limitations in (S)TEM imaging of polymers and composites.

    PubMed

    Gnanasekaran, Karthikeyan; Snel, Roderick; de With, Gijsbertus; Friedrich, Heiner

    2016-01-01

    Sampling limitations in electron microscopy questions whether the analysis of a bulk material is representative, especially while analyzing hierarchical morphologies that extend over multiple length scales. We tackled this problem by automatically acquiring a large series of partially overlapping (S)TEM images with sufficient resolution, subsequently stitched together to generate a large-area map using an in-house developed acquisition toolbox (TU/e Acquisition ToolBox) and stitching module (TU/e Stitcher). In addition, we show that quantitative image analysis of the large scale maps provides representative information that can be related to the synthesis and process conditions of hierarchical materials, which moves electron microscopy analysis towards becoming a bulk characterization tool. We demonstrate the power of such an analysis by examining two different multi-phase materials that are structured over multiple length scales. PMID:26492325

  18. Limitations of indium leukocyte imaging for the diagnosis of spine infections

    SciTech Connect

    Whalen, J.L.; Brown, M.L.; McLeod, R.; Fitzgerald, R.H. Jr. )

    1991-02-01

    The usefulness of indium-111 white blood cell (WBC) scintigraphy in the detection of spine sepsis was studied in 22 patients who had open or percutaneous biopsies for microbiologic diagnosis. The indium images in 18 patients with vertebral infection were falsely negative in 15 (83%) and truly positive in 3 (17%). All four patients with negative cultures and histology had true-negative scans. The indium-111 WBC imaging results yielded a sensitivity of 17%, a specificity of 100%, and an accuracy rate of 31%. Prior antibiotic therapy was correlated with a high incidence of false-negative scans and photon-deficient indium-111 WBC uptake. The usefulness of indium-111 WBC scintigraphy for the diagnosis of vertebral infection may be limited to those patients who have not been treated with antibiotics previously.

  19. Noninvasive Imaging of 3D Dynamics in Thickly Fluorescent Specimens Beyond the Diffraction Limit

    PubMed Central

    Gao, Liang; Shao, Lin; Higgins, Christopher D.; Poulton, John S.; Peifer, Mark; Davidson, Michael W.; Wu, Xufeng; Goldstein, Bob; Betzig, Eric

    2013-01-01

    SUMMARY Optical imaging of the dynamics of living specimens involves tradeoffs between spatial resolution, temporal resolution, and phototoxicity, made more difficult in three-dimensions. Here, however, we report that rapid 3D dynamics can be studied beyond the diffraction limit in thick or densely fluorescent living specimens over many time points by combining ultra-thin planar illumination produced by scanned Bessel beams with superresolution structured illumination microscopy. We demonstrate in vivo karyotyping of chromosomes during mitosis and identify different dynamics for the actin cytoskeleton at the dorsal and ventral surfaces of fibroblasts. Compared to spinning disk confocal microscopy, we demonstrate substantially reduced photodamage when imaging rapid morphological changes in D. discoideum cells, as well as improved contrast and resolution at depth within developing C. elegans embryos. Bessel beam structured plane illumination thus promises new insights into complex biological phenomena that require 4D subcellular spatiotemporal detail in either a single or multicellular context. PMID:23217717

  20. FRIDA, the diffraction limited NIR imager and IFS for the Gran Telescopio Canarias: status report

    NASA Astrophysics Data System (ADS)

    López, J. A.; Acosta, J.; Alvarez, L. C.; Bringas, V.; Cardiel, N.; Clark, D. M.; Corrales, A.; Cuevas, S.; Chapa, O.; Díaz Garcia, J. J.; Eikenberry, S. S.; Eliche, C.; Espejo, C.; Flores, R.; Fuentes, J.; Gallego, J.; Garcés, J.; Garzón, F.; Hammersley, P.; Keiman, C.; Lara, G.; López, P.; Lucero, D.; Moreno, H.; Pascual, S.; Patrón, J.; Prieto, A.; Rodríguez, A.; Rodríguez, B.; Sánchez, B.; Torres, D.; Uribe, J.; Watson, A.

    2014-07-01

    FRIDA is a diffraction limited imager and integral field spectrometer that is being built for the Gran Telescopio Canarias. FRIDA has been designed and is being built as a collaborative project between institutions from México, Spain and the USA. In imaging mode FRIDA will provide scales of 0.010, 0.020 and 0.040 arcsec/pixel and in IFS mode spectral resolutions R ~ 1000, 4,500 and 30,000. FRIDA is starting systems integration and is scheduled to complete fully integrated system tests at the laboratory by the end of 2015 and be delivered to GTC shortly after. In this contribution we present a summary of its design, fabrication, current status and potential scientific applications.

  1. The image charge effect and vibron-assisted processes in Coulomb blockade transport: a first principles approach

    NASA Astrophysics Data System (ADS)

    Souza, A. M.; Rungger, I.; Schwingenschlögl, U.; Sanvito, S.

    2015-11-01

    We present a combination of density functional theory and of both non-equilibrium Green's function formalism and a Master equation approach to accurately describe quantum transport in molecular junctions in the Coulomb blockade regime. We apply this effective first-principles approach to reproduce the experimental results of Perrin et al., [Nat. Nanotechnol., 2013, 8, 282] for the transport properties of a Au-(Zn)porphyrin-Au molecular junction. We demonstrate that energy level renormalization due to the image charge effect is crucial to the prediction of the current onset in the current-voltage, I-V, curves as a function of electrode separation. Furthermore, we show that for voltages beyond that setting the current onset, the slope of the I-V characteristics is determined by the interaction of the charge carriers with molecular vibrations. This corresponds to current-induced local heating, which may also lead to an effective reduced electronic coupling. Overall our scheme provides a fully ab initio description of quantum transport in the Coulomb blockade regime in the presence of electron-vibron coupling.We present a combination of density functional theory and of both non-equilibrium Green's function formalism and a Master equation approach to accurately describe quantum transport in molecular junctions in the Coulomb blockade regime. We apply this effective first-principles approach to reproduce the experimental results of Perrin et al., [Nat. Nanotechnol., 2013, 8, 282] for the transport properties of a Au-(Zn)porphyrin-Au molecular junction. We demonstrate that energy level renormalization due to the image charge effect is crucial to the prediction of the current onset in the current-voltage, I-V, curves as a function of electrode separation. Furthermore, we show that for voltages beyond that setting the current onset, the slope of the I-V characteristics is determined by the interaction of the charge carriers with molecular vibrations. This corresponds to

  2. Limits on the neutrino velocity, Lorentz invariance, and the weak equivalence principle with TeV neutrinos from gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Wei, Jun-Jie; Wu, Xue-Feng; Gao, He; Mészáros, Peter

    2016-08-01

    Five TeV neutrino events weakly correlated with five gamma-ray bursts (GRBs) were detected recently by IceCube. This work is an attempt to show that if the GRB identifications are verified, the observed time delays between the TeV neutrinos and gamma-ray photons from GRBs provide attractive candidates for testing fundamental physics with high accuracy. Based on the assumed associations between the TeV neutrinos and GRBs, we find that the limiting velocity of the neutrinos is equal to that of photons to an accuracy of ~ 1.9 × 10‑15 – 2.5 × 10‑18, which is about 104 – 107 times better than the constraint obtained with the neutrino possibly from a blazar flare. In addition, we set the most stringent limits up to date on the energy scale of quantum gravity for both the linear and quadratic violations of Lorentz invariance, namely EQG, 1 > 6.3 × 1018 – 1.5 × 1021 GeV and EQG, 2 > 2.0 × 1011 – 4.2 × 1012 GeV, which are essentially as good as or are an improvement of one order of magnitude over the results previously obtained by the GeV photons of GRB 090510 and the PeV neutrino from a blazar flare. Assuming that the Shapiro time delay is caused by the gravitational potential of the Laniakea supercluster of galaxies, we also place the tightest limits to date on Einstein's weak equivalence principle through the relative differential variations of the parameterized post-Newtonian parameter γ values for two different species of particles (i.e., neutrinos and photons), yielding Δγ ~ 10‑11 – 10‑13. However, it should be emphasized again that these limits here obtained are at best forecast of what could be achieved if the GRB/neutrino correlations would be finally confirmed.

  3. Interferometric backward third harmonic generation microscopy for axial imaging with accuracy beyond the diffraction limit.

    PubMed

    Sandkuijl, Daaf; Kontenis, Lukas; Coelho, Nuno M; McCulloch, Christopher; Barzda, Virginijus

    2014-01-01

    A new nonlinear microscopy technique based on interference of backward-reflected third harmonic generation (I-THG) from multiple interfaces is presented. The technique is used to measure height variations or changes of a layer thickness with an accuracy of up to 5 nm. Height variations of a patterned glass surface and thickness variations of fibroblasts are visualized with the interferometric epi-THG microscope with an accuracy at least two orders of magnitude better than diffraction limit. The microscopy technique can be broadly applied for measuring distance variations between membranes or multilayer structures inside biological tissue and for surface height variation imaging. PMID:24710103

  4. High resolution imaging beyond the acoustic diffraction limit in deep tissue via ultrasound-switchable NIR fluorescence

    NASA Astrophysics Data System (ADS)

    Pei, Yanbo; Wei, Ming-Yuan; Cheng, Bingbing; Liu, Yuan; Xie, Zhiwei; Nguyen, Kytai; Yuan, Baohong

    2014-04-01

    Fluorescence imaging in deep tissue with high spatial resolution is highly desirable because it can provide details about tissue's structural, functional, and molecular information. Unfortunately, current fluorescence imaging techniques are limited either in penetration depth (microscopy) or spatial resolution (diffuse light based imaging) as a result of strong light scattering in deep tissue. To overcome this limitation, we developed an ultrasound-switchable fluorescence (USF) imaging technique whereby ultrasound was used to switch on/off the emission of near infrared (NIR) fluorophores. We synthesized and characterized unique NIR USF contrast agents. The excellent switching properties of these agents, combined with the sensitive USF imaging system developed in this study, enabled us to image fluorescent targets in deep tissue with spatial resolution beyond the acoustic diffraction limit.

  5. Cooperative effects for measurement: Raman superradiance imaging and quantum states for Heisenberg limited interferometry

    NASA Astrophysics Data System (ADS)

    Uys, Hermann

    Cooperative effects in many-particle systems can be exploited to achieve measurement outcomes not possible with independent probe particles. We explore two measurement applications based on the cooperative phenomenon of superradiance or on correlated quantum states closely related to superradiance. In the first application we study the off-resonant superradiant Raman scattering of light from an ultracold Bose atomic vapor. We investigate the temperature dependence of superradiance for a trapped vapor and show that in the regime where superradiance occurs on a timescale comparable to a trap frequency, scattering takes place preferentially from atoms in the lowest trap levels due to Doppler dephasing. As a consequence, below the critical temperature for Bose condensation, absorption images of transmitted light serve as a direct probe of the condensed state. Subsequently, we consider a pure condensate and study the time-dependent spatial features of transmitted light, obtaining good qualitative agreement with recent imaging experiments. Inclusion of quantum fluctuations in the initial stages of the superradiant emission accounts well for shot-to-shot fluctuations. Secondly, we have used simulated annealing, a global optimization strategy, to systematically search for correlated quantum interferometer input states that approach the Heisenberg limited uncertainty in estimates of the interferometer phase shift. That limit improves over the standard quantum limit to the phase sensitivity of interferometric measurements by a factor of 1/ N , where N is the number of interfering particles. We compare the performance of these states to that of other non-classical states already known to yield Heisenberg limited uncertainty.

  6. Novel techniques for detection and imaging of spin related phenomena: Towards sub-diffraction limited resolution

    NASA Astrophysics Data System (ADS)

    Wolfe, Christopher Stuart

    The idea that the spin degree of freedom of particles can be used to store and transport information has revolutionized the data storage industry and inspired a huge amount of research activity. Spin electronics, or spintronics, provides a plethora of potential improvements to conventional charge electronics that include increased functionality and energy efficiency. Scientists studying spintronics will need a multitude of characterization tools to sensitively detect spins in new materials and devices. There are already a handful of powerful techniques to image spin-related phenomena, but each has limitations. Magnetic resonance force microscopy, for example, offers sensitive detection of spin moments that are localized or nearly so but requires a high vacuum, cryogenic environment. Magnetometry based on nitrogen vacancy centers in diamond is a powerful approach, but requires the nitrogen vacancy center to be in very close contact to the spin system being studied to be able to measure the field generated by the system. Spin-polarized scanning tunneling microscopy provides perhaps the best demonstrated spatial resolution, but typically requires ultrahigh vacuum conditions and is limited to studying the surface of a sample. Traditional optical techniques such as Faraday or Kerr microscopy are limited in spatial resolution by the optical diffraction limit. In this dissertation I will present three new techniques we have developed to address some of these issues and to provide the community with new tools to help push forward spintronics and magnetism related research. I will start by presenting the first experimental demonstration of scanned spin-precession microscopy. This technique has the potential to turn any spin-sensitive detection technique into an imaging platform by providing the groundwork for incorporating a magnetic field gradient with that technique, akin to magnetic resonance imaging, and the mathematical tools to analyze the data and extract the local

  7. The image charge effect and vibron-assisted processes in Coulomb blockade transport: a first principles approach.

    PubMed

    Souza, A M; Rungger, I; Schwingenschlögl, U; Sanvito, S

    2015-12-01

    We present a combination of density functional theory and of both non-equilibrium Green's function formalism and a Master equation approach to accurately describe quantum transport in molecular junctions in the Coulomb blockade regime. We apply this effective first-principles approach to reproduce the experimental results of Perrin et al., [Nat. Nanotechnol., 2013, 8, 282] for the transport properties of a Au-(Zn)porphyrin-Au molecular junction. We demonstrate that energy level renormalization due to the image charge effect is crucial to the prediction of the current onset in the current-voltage, I-V, curves as a function of electrode separation. Furthermore, we show that for voltages beyond that setting the current onset, the slope of the I-V characteristics is determined by the interaction of the charge carriers with molecular vibrations. This corresponds to current-induced local heating, which may also lead to an effective reduced electronic coupling. Overall our scheme provides a fully ab initio description of quantum transport in the Coulomb blockade regime in the presence of electron-vibron coupling. PMID:26525140

  8. Quantitative in vivo cell-surface receptor imaging in oncology: kinetic modeling & paired-agent principles from nuclear medicine and optical imaging

    PubMed Central

    Tichauer, Kenneth M.; Wang, Yu; Pogue, Brian W.; Liu, Jonathan T. C.

    2015-01-01

    The development of methods to accurately quantify cell-surface receptors in living tissues would have a seminal impact in oncology. For example, accurate measures of receptor density in vivo could enhance early detection or surgical resection of tumors via protein-based contrast, allowing removal of cancer with high phenotype specificity. Alternatively, accurate receptor expression estimation could be used as a biomarker to guide patient-specific clinical oncology targeting of the same molecular pathway. Unfortunately, conventional molecular contrast-based imaging approaches are not well adapted to accurately estimating the nanomolar-level cell-surface receptor concentrations in tumors, as most images are dominated by nonspecific sources of contrast such as high vascular permeability and lymphatic inhibition. This article reviews approaches for overcoming these limitations based upon tracer kinetic modeling and the use of emerging protocols to estimate binding potential and the related receptor concentration. Methods such as using single time point imaging or a reference-tissue approach tend to have low accuracy in tumors, whereas paired-agent methods or advanced kinetic analyses are more promising to eliminate the dominance of interstitial space in the signals. Nuclear medicine and optical molecular imaging are the primary modalities used, as they have the nanomolar level sensitivity needed to quantify cell-surface receptor concentrations present in tissue, although each likely has a different clinical niche. PMID:26134619

  9. Quantitative in vivo cell-surface receptor imaging in oncology: kinetic modeling and paired-agent principles from nuclear medicine and optical imaging

    NASA Astrophysics Data System (ADS)

    Tichauer, Kenneth M.; Wang, Yu; Pogue, Brian W.; Liu, Jonathan T. C.

    2015-07-01

    The development of methods to accurately quantify cell-surface receptors in living tissues would have a seminal impact in oncology. For example, accurate measures of receptor density in vivo could enhance early detection or surgical resection of tumors via protein-based contrast, allowing removal of cancer with high phenotype specificity. Alternatively, accurate receptor expression estimation could be used as a biomarker to guide patient-specific clinical oncology targeting of the same molecular pathway. Unfortunately, conventional molecular contrast-based imaging approaches are not well adapted to accurately estimating the nanomolar-level cell-surface receptor concentrations in tumors, as most images are dominated by nonspecific sources of contrast such as high vascular permeability and lymphatic inhibition. This article reviews approaches for overcoming these limitations based upon tracer kinetic modeling and the use of emerging protocols to estimate binding potential and the related receptor concentration. Methods such as using single time point imaging or a reference-tissue approach tend to have low accuracy in tumors, whereas paired-agent methods or advanced kinetic analyses are more promising to eliminate the dominance of interstitial space in the signals. Nuclear medicine and optical molecular imaging are the primary modalities used, as they have the nanomolar level sensitivity needed to quantify cell-surface receptor concentrations present in tissue, although each likely has a different clinical niche.

  10. First-principles analysis of the spectroscopic limited maximum efficiency of photovoltaic absorber layers for CuAu-like chalcogenides and silicon.

    PubMed

    Bercx, Marnik; Sarmadian, Nasrin; Saniz, Rolando; Partoens, Bart; Lamoen, Dirk

    2016-07-27

    Chalcopyrite semiconductors are of considerable interest for application as absorber layers in thin-film photovoltaic cells. When growing films of these compounds, however, they are often found to contain CuAu-like domains, a metastable phase of chalcopyrite. It has been reported that for CuInS2, the presence of the CuAu-like phase improves the short circuit current of the chalcopyrite-based photovoltaic cell. We investigate the thermodynamic stability of both phases for a selected list of I-III-VI2 materials using a first-principles density functional theory approach. For the CuIn-VI2 compounds, the difference in formation energy between the chalcopyrite and CuAu-like phase is found to be close to 2 meV per atom, indicating a high likelihood of the presence of CuAu-like domains. Next, we calculate the spectroscopic limited maximum efficiency (SLME) of the CuAu-like phase and compare the results with those of the corresponding chalcopyrite phase. We identify several candidates with a high efficiency, such as CuAu-like CuInS2, for which we obtain an SLME of 29% at a thickness of 500 nm. We observe that the SLME can have values above the Shockley-Queisser (SQ) limit, and show that this can occur because the SQ limit assumes the absorptivity to be a step function, thus overestimating the radiative recombination in the detailed balance approach. This means that it is possible to find higher theoretical efficiencies within this framework simply by calculating the J-V characteristic with an absorption spectrum. Finally, we expand our SLME analysis to indirect band gap absorbers by studying silicon, and find that the SLME quickly overestimates the reverse saturation current of indirect band gap materials, drastically lowering their calculated efficiency. PMID:27405243

  11. The First Diffraction-Limited Images from the W. M. Keck Telescope

    NASA Technical Reports Server (NTRS)

    Matthews, K.; Ghez, A. M.; Weinberger, A. J.; Neugebauer, G.

    1996-01-01

    The first diffraction limited, 0.05s resolution, images on the W. M. Keck Telescope have been obtained at a wavelength of 2.2 micrometers. These images were part of an experiment to test the suitability of the Keck Telescope for speckle imaging. In order to conduct this test, it was necessary to modify the pixel scale of the Keck facility Near Infrared Camera (NIRC) to optimally sample the spatial frequencies made available by the Keck telescope. The design and implementation of the external reimaging optics, which convert the standard fl25 beam from the secondary mirror to fl182, are described here. Techniques for reducing speckle data with field rotation on an alt-az telescope are also described. Three binary stars were observed in this experiment with separations as small as 0.05s. With only 100 frames of data on each, a dynamic range of at least 3.5 mag was achieved in all cases. These observations imply that a companion as faint as 14.5 mag at 2.2 micrometers could be detected around an 11th magnitude point source.

  12. Folate Receptor-Beta Has Limited Value for Fluorescent Imaging in Ovarian, Breast and Colorectal Cancer

    PubMed Central

    de Boer, Esther; van der Vegt, Bert; van der Sluis, Tineke; Kooijman, Paulien; Low, Philip S.; van der Zee, Ate G. J.; Arts, Henriette J. G.; van Dam, Gooitzen M.; Bart, Joost

    2015-01-01

    Aims Tumor-specific targeted imaging is rapidly evolving in cancer diagnosis. The folate receptor alpha (FR-α) has already been identified as a suitable target for cancer therapy and imaging. FR-α is present on ~40% of human cancers. FR-β is known to be expressed on several hematologic malignancies and on activated macrophages, but little is known about FR-β expression in solid tumors. Additional or simultaneous expression of FR-β could help extend the indications for folate-based drugs and imaging agents. In this study, the expression pattern of FR-β is evaluated in ovarian, breast and colorectal cancer. Methods FR-β expression was analyzed by semi-quantitative scoring of immunohistochemical staining on tissue microarrays (TMAs) of 339 ovarian cancer patients, 418 breast cancer patients, on 20 slides of colorectal cancer samples and on 25 samples of diverticulitis. Results FR-β expression was seen in 21% of ovarian cancer samples, 9% of breast cancer samples, and 55% of colorectal cancer samples. Expression was weak or moderate. Of the diverticulitis samples, 80% were positive for FR-β expression in macrophages. FR-β status neither correlated to known disease-related variables, nor showed association with overall survival and progression free survival in ovarian and breast cancer. In breast cancer, negative axillary status was significantly correlated to FR-β expression (p=0.022). Conclusions FR-β expression was low or absent in the majority of ovarian, breast and colorectal tumor samples. From the present study we conclude that the low FR-β expression in ovarian and breast tumor tissue indicates limited practical use of this receptor in diagnostic imaging and therapeutic purposes. Due to weak expression, FR-β is not regarded as a suitable target in colorectal cancer. PMID:26248049

  13. Diffraction-limited Polarimetry from the Infrared Imaging Magnetograph at Big Bear Solar Observatory

    NASA Astrophysics Data System (ADS)

    Cao, Wenda; Jing, Ju; Ma, Jun; Xu, Yan; Wang, Haimin; Goode, Philip R.

    2006-06-01

    The Infrared Imaging Magnetograph (IRIM) system developed by Big Bear Solar Observatory (BBSO) has been put into preliminary operation. It is one of the first imaging spectropolarimeters working at 1565 nm and is used for the observations of the Sun at its opacity minimum, exposing the deepest photospheric layers. The tandem system, which includes a 4.2 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Pérot etalon, is capable of providing a bandpass as low as 0.01 nm in a telecentric configuration. A fixed quarter-wave plate and a nematic liquid crystal variable retarder are employed for analyzing the circular polarization of the Zeeman components. The longitudinal magnetic field is measured for the highly Zeeman-sensitive Fe I line at 1564.85 nm (Landé factor g=3). The polarimetric data were taken through a field of view of ~145''×145'' and were recorded by a 1024×1024 pixel, 14 bit HgCdTe CMOS focal plane array camera. Benefiting from the correlation tracking system and a newly developed adaptive optics system, the first imaging polarimetric observations at 1565 nm were made at the diffraction limit on 2005 July 1 using BBSO's 65 cm telescope. After comparing the magnetograms from IRIM with those taken by the Michelson Doppler Imager on board SOHO, it was found that all the magnetic features matched very well in both sets of magnetograms. In addition, Stokes V profiles obtained from the Fabry-Pérot etalon scan data provide access to both the true magnetic field strength and the filling factor of the small-scale magnetic flux elements. In this paper, we present the design, fabrication, and calibration of IRIM, as well as the results of the first scientific observations.

  14. Use of frozen-hydrated axonemes to assess imaging parameters and resolution limits in cryoelectron tomography.

    PubMed

    McEwen, Bruce F; Marko, Michael; Hsieh, Chyong-Ere; Mannella, Carmen

    2002-01-01

    Using a 400-kV cryoelectron microscope, we have obtained tomographic reconstructions of frozen-hydrated sea urchin axonemes with 8-10-nm resolution, as assessed by detection of characteristic components including doublet microtubules, radial spokes, central sheath projections, and outer dynein arms. We did not detect the inner dynein arms or the microtubule lattice. The 1/(8 nm) and 1/(16 nm) layer lines are consistently present in power spectra of both projection images and tomographic reconstructions. Strength and detection of the layer lines are dependent upon total electron dose and defocus. Both layer lines are surprisingly resistant to electron doses of up to 11000 electrons/nm(2). We present a summary of resolution considerations in cryoelectron tomography and conclude that the fundamental limitation is the total electron dose required for statistical significance. The electron dose can be fractionated among the numerous angular views in a tomographic data set, but there is an unavoidable fourth-power dependence of total dose on target resolution. Since higher-resolution features are more beam-sensitive, this dose requirement places an ultimate limit on the resolution of individual tomographic reconstructions. Instrumental and computational strategies to circumvent this limitation are discussed. PMID:12160700

  15. Geomorphic classification of Icelandic and Martian volcanoes: Limitations of comparative planetology research from LANDSAT and Viking orbiter images

    NASA Technical Reports Server (NTRS)

    Williams, R. S., Jr.

    1985-01-01

    Some limitations in using orbital images of planetary surfaces for comparative landform analyses are discussed. The principal orbital images used were LANDSAT MSS images of Earth and nominal Viking Orbiter images of Mars. Both are roughly comparable in having a pixel size which corresponds to about 100 m on the planetary surface. A volcanic landform on either planet must have a horizontal dimension of at least 200 m to be discernible on orbital images. A twofold bias is directly introduced into any comparative analysis of volcanic landforms on Mars versus those in Iceland because of this scale limitation. First, the 200-m cutoff of landforms may delete more types of volcanic landforms on Earth than on Mars or vice versa. Second, volcanic landforms in Iceland, too small to be resolved or orbital images, may be represented by larger counterparts on Mars or vice versa.

  16. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trades offs

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Norman, Colin Arthur; Soummer, Remi; Perrin, Marshall D.; N'Diaye, Mamadou; Choquet, Elodie

    2015-01-01

    In a recent paper we discussed a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach, named Active Compensation of Aperture Discontinuities (ACAD) relies on two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum. In particular we showed that broadband high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies for a variety of telescope pupil geometries. In this paper we first focus on the fundamental limits and practical trade-offs associated with ACAD. In a first part we will study the fundamental limits and practical tradeoffs associated with ACAD, regardless of the downstream coronagraphic architecture. The mathematical techniques to finding ACAD DM shapes require to solve a complex differential equation. We will first discuss the scaling laws underlying this non-linear solution and their impact of DM placement and geometry wishing the optical design of an instrument. We will then consider the sensitivity to low order aberrations: in principle an ACAD solution that comprises large strokes will be more sensitive to these aberrations than one with smaller strokes. As a consequence, we will quantify this sensitive both using analytical models and numerical simulations. We will present diffractive end to end simulations and quantify the ultimate contrast and bandwidth achievable with ACAD, which can be reached by superposing using a classical linear wavefront control algorithms on top of the Monge Ampere solution. Finally, recent work has shown that coronagraph designs can also accommodate for secondary support structures and/or segments gaps, at a

  17. Fundamental x-ray interaction limits in diagnostic imaging detectors: spatial resolution.

    PubMed

    Hajdok, G; Battista, J J; Cunningham, I A

    2008-07-01

    The practice of diagnostic x-ray imaging has been transformed with the emergence of digital detector technology. Although digital systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. The authors present a Monte Carlo study to determine fundamental resolution limits caused by x-ray interactions in four converter materials: Amorphous silicon (a-Si), amorphous selenium, cesium iodide, and lead iodide. The "x-ray interaction" modulation transfer function (MTF) was determined for each material and compared in terms of the 50% MTF spatial frequency and Wagner's effective aperture for incident photon energies between 10 and 150 keV and various converter thicknesses. Several conclusions can be drawn from their Monte Carlo study. (i) In low-Z (a-Si) converters, reabsorption of Compton scatter x rays limits spatial resolution with a sharp MTF drop at very low spatial frequencies (< 0.3 cycles/mm), especially above 60 keV; while in high-Z materials, reabsorption of characteristic x rays plays a dominant role, resulting in a mid-frequency (1-5 cycles/mm) MTF drop. (ii) Coherent scatter plays a minor role in the x-ray interaction MTF. (iii) The spread of energy due to secondary electron (e.g., photoelectrons) transport is significant only at very high spatial frequencies. (iv) Unlike the spread of optical light in phosphors, the spread of absorbed energy from x-ray interactions does not significantly degrade spatial resolution as converter thickness is increased. (v) The effective aperture results reported here represent fundamental spatial resolution limits of the materials tested and serve as target benchmarks for the design and development of future digital x-ray detectors. PMID:18697543

  18. Fundamental x-ray interaction limits in diagnostic imaging detectors: Spatial resolution

    SciTech Connect

    Hajdok, G.; Battista, J. J.; Cunningham, I. A.

    2008-07-15

    The practice of diagnostic x-ray imaging has been transformed with the emergence of digital detector technology. Although digital systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. The authors present a Monte Carlo study to determine fundamental resolution limits caused by x-ray interactions in four converter materials: Amorphous silicon (a-Si), amorphous selenium, cesium iodide, and lead iodide. The ''x-ray interaction'' modulation transfer function (MTF) was determined for each material and compared in terms of the 50% MTF spatial frequency and Wagner's effective aperture for incident photon energies between 10 and 150 keV and various converter thicknesses. Several conclusions can be drawn from their Monte Carlo study. (i) In low-Z (a-Si) converters, reabsorption of Compton scatter x rays limits spatial resolution with a sharp MTF drop at very low spatial frequencies (<0.3 cycles/mm), especially above 60 keV; while in high-Z materials, reabsorption of characteristic x rays plays a dominant role, resulting in a mid-frequency (1-5 cycles/mm) MTF drop. (ii) Coherent scatter plays a minor role in the x-ray interaction MTF. (iii) The spread of energy due to secondary electron (e.g., photoelectrons) transport is significant only at very high spatial frequencies. (iv) Unlike the spread of optical light in phosphors, the spread of absorbed energy from x-ray interactions does not significantly degrade spatial resolution as converter thickness is increased. (v) The effective aperture results reported here represent fundamental spatial resolution limits of the materials tested and serve as target benchmarks for the design and development of future digital x-ray detectors.

  19. The limit of detection in scintigraphic imaging with I-131 in patients with differentiated thyroid carcinoma

    NASA Astrophysics Data System (ADS)

    Hänscheid, H.; Lassmann, M.; Buck, A. K.; Reiners, C.; Verburg, F. A.

    2014-05-01

    Radioiodine scintigraphy influences staging and treatment in patients with differentiated thyroid carcinoma. The limit of detection for fractional uptake in an iodine avid focus in a scintigraphic image was determined from the number of lesion net counts and the count density of the tissue background. The count statistics were used to calculate the diagnostic activity required to elevate the signal from a lesion with a given uptake significantly above a homogeneous background with randomly distributed counts per area. The dependences of the minimal uptake and the minimal size of lesions visible in a scan on several parameters of influence were determined by linking the typical biokinetics observed in iodine avid tissue to the lesion mass and to the absorbed dose received in a radioiodine therapy. The detection limits for fractional uptake in a neck lesion of a typical patient are about 0.001% after therapy with 7000 MBq, 0.01% for activities typically administered in diagnostic assessments (74-185 MBq), and 0.1% after the administration of 10 MBq I-131. Lesions at the limit of detection in a diagnostic scan with biokinetics eligible for radioiodine therapy are small with diameters of a few millimeters. Increasing the diagnostic activity by a factor of 4 reduces the diameter of visible lesions by 25% or about 1 mm. Several other determinants have a comparable or higher influence on the limit of detection than the administered activity; most important are the biokinetics in both blood pool and target tissue and the time of measurement. A generally valid recommendation for the timing of the scan is impossible as the time of the highest probability to detect iodine avid tissue depends on the administered activity as well as on the biokinetics in the lesion and background in the individual patient.

  20. Optical Imaging of Nonuniform Ferroelectricity and Strain at the Diffraction Limit.

    PubMed

    Vlasin, Ondrej; Casals, Blai; Dix, Nico; Gutiérrez, Diego; Sánchez, Florencio; Herranz, Gervasi

    2015-01-01

    We have imaged optically the spatial distributions of ferroelectricity and piezoelectricity at the diffraction limit. Contributions to the birefringence from electro-optics--linked to ferroelectricity--as well as strain--arising from converse piezoelectric effects--have been recorded simultaneously in a BaTiO3 thin film. The concurrent recording of electro-optic and piezo-optic mappings revealed that, far from the ideal uniformity, the ferroelectric and piezoelectric responses were strikingly inhomogeneous, exhibiting significant fluctuations over the scale of the micrometer. The optical methods here described are appropriate to study the variations of these properties simultaneously, which are of great relevance when ferroelectrics are downscaled to small sizes for applications in data storage and processing. PMID:26522345

  1. Optical Imaging of Nonuniform Ferroelectricity and Strain at the Diffraction Limit

    PubMed Central

    Vlasin, Ondrej; Casals, Blai; Dix, Nico; Gutiérrez, Diego; Sánchez, Florencio; Herranz, Gervasi

    2015-01-01

    We have imaged optically the spatial distributions of ferroelectricity and piezoelectricity at the diffraction limit. Contributions to the birefringence from electro-optics –linked to ferroelectricity– as well as strain –arising from converse piezoelectric effects– have been recorded simultaneously in a BaTiO3 thin film. The concurrent recording of electro-optic and piezo-optic mappings revealed that, far from the ideal uniformity, the ferroelectric and piezoelectric responses were strikingly inhomogeneous, exhibiting significant fluctuations over the scale of the micrometer. The optical methods here described are appropriate to study the variations of these properties simultaneously, which are of great relevance when ferroelectrics are downscaled to small sizes for applications in data storage and processing. PMID:26522345

  2. Image recovery techniques for x-ray computed tomography in limited data environments

    SciTech Connect

    Aufderheide, M B; Goodman, D M; Jackson, J A; Johansson, E M

    1999-03-01

    There is an increasing requirement throughout LLNL for nondestructive evaluation using X-ray computed tomography (CT). In many cases, restrictions on data acquisition time, imaging geometry, and budgets make it unfeasible to acquire projection data over enough views to achieve desired spatial resolution using conventional CT methods. In particular, conventional CT methods are non-iterative algorithms that have the advantage of low computational effort, but they are not sufficiently adaptable to incorporate prior information or non-Gaussian statistics. Most currently existing iterative tomography algorithms are based on methods that are time consuming because they converge very flowingly, if at all. The goal of the work was to develop a set of limited data CT reconstruction tools and then demonstrate their usefulness by applying them to a variety of problems of interest to LLNL. In this project they continued their development of reconstruction tools and they have demonstrated their effectiveness on several important problems.

  3. A line-imaging velocity interferometer technique for shock diagnostics without x-ray preheat limitation.

    PubMed

    Wang, Feng; Peng, Xiaoshi; Liu, Shenye; Xu, Tao; Mei, Lusheng; Jiang, Xiaohua; Ding, Yongkun

    2011-10-01

    A study was conducted with a line-imaging velocity interferometer on sandwich targets at the Shen Guang-III prototype laser facility in China, with the goal of eliminating the preheat effect. A sandwich target structure was used to reduce the x-ray preheat limitation (radiation temperature ~170 eV) in a radiative drive shock experiment. With a thick ablator, the preheat effect appeared before the shock arrived at the window. After adding a shield layer of high-Z material on the ablator, x-rays which penetrated the ablator were so weak that the blank-out effect could not be measured. This experiment indicates that the sandwich target may provide a valuable technique in experiments such as equation of state and shock timing for inertial confinement fusion studies. PMID:22047281

  4. Iterative optimizing quantization method for reconstructing three-dimensional images from a limited number of views

    DOEpatents

    Lee, H.R.

    1997-11-18

    A three-dimensional image reconstruction method comprises treating the object of interest as a group of elements with a size that is determined by the resolution of the projection data, e.g., as determined by the size of each pixel. One of the projections is used as a reference projection. A fictitious object is arbitrarily defined that is constrained by such reference projection. The method modifies the known structure of the fictitious object by comparing and optimizing its four projections to those of the unknown structure of the real object and continues to iterate until the optimization is limited by the residual sum of background noise. The method is composed of several sub-processes that acquire four projections from the real data and the fictitious object: generate an arbitrary distribution to define the fictitious object, optimize the four projections, generate a new distribution for the fictitious object, and enhance the reconstructed image. The sub-process for the acquisition of the four projections from the input real data is simply the function of acquiring the four projections from the data of the transmitted intensity. The transmitted intensity represents the density distribution, that is, the distribution of absorption coefficients through the object. 5 figs.

  5. Iterative optimizing quantization method for reconstructing three-dimensional images from a limited number of views

    DOEpatents

    Lee, Heung-Rae

    1997-01-01

    A three-dimensional image reconstruction method comprises treating the object of interest as a group of elements with a size that is determined by the resolution of the projection data, e.g., as determined by the size of each pixel. One of the projections is used as a reference projection. A fictitious object is arbitrarily defined that is constrained by such reference projection. The method modifies the known structure of the fictitious object by comparing and optimizing its four projections to those of the unknown structure of the real object and continues to iterate until the optimization is limited by the residual sum of background noise. The method is composed of several sub-processes that acquire four projections from the real data and the fictitious object: generate an arbitrary distribution to define the fictitious object, optimize the four projections, generate a new distribution for the fictitious object, and enhance the reconstructed image. The sub-process for the acquisition of the four projections from the input real data is simply the function of acquiring the four projections from the data of the transmitted intensity. The transmitted intensity represents the density distribution, that is, the distribution of absorption coefficients through the object.

  6. Phonon-limited resistivity of graphene by first-principles calculations: Electron-phonon interactions, strain-induced gauge field, and Boltzmann equation

    NASA Astrophysics Data System (ADS)

    Sohier, Thibault; Calandra, Matteo; Park, Cheol-Hwan; Bonini, Nicola; Marzari, Nicola; Mauri, Francesco

    2014-09-01

    We use first-principles calculations, at the density-functional-theory (DFT) and GW levels, to study both the electron-phonon interaction for acoustic phonons and the "synthetic" vector potential induced by a strain deformation (responsible for an effective magnetic field in case of a nonuniform strain). In particular, the interactions between electrons and acoustic phonon modes, the so-called gauge-field and deformation potential, are calculated at the DFT level in the framework of linear response. The zero-momentum limit of acoustic phonons is interpreted as a strain of the crystal unit cell, allowing the calculation of the acoustic gauge-field parameter (synthetic vector potential) within the GW approximation as well. We find that using an accurate model for the polarizations of the acoustic phonon modes is crucial to obtain correct numerical results. Similarly, in the presence of a strain deformation, the relaxation of atomic internal coordinates cannot be neglected. The role of electronic screening on the electron-phonon matrix elements is carefully investigated. We then solve the Boltzmann equation semianalytically in graphene, including both acoustic and optical phonon scattering. We show that, in the Bloch-Grüneisen and equipartition regimes, the electronic transport is mainly ruled by the unscreened acoustic gauge field, while the contribution due to the deformation potential is negligible and strongly screened. We show that the contribution of acoustic phonons to resistivity is doping and substrate independent, in agreement with experimental observations. The first-principles calculations, even at the GW level, underestimate this contribution to resistivity by ≈30%. At high temperature (T >270 K), the calculated resistivity underestimates the experimental one more severely, the underestimation being larger at lower doping. We show that, besides remote phonon scattering, a possible explanation for this disagreement is the electron-electron interaction

  7. Role of Diffusion-weighted Imaging in Acute Stroke Management using Low-field Magnetic Resonance Imaging in Resource-limited Settings

    PubMed Central

    Okorie, Chinonye K; Ogbole, Godwin I; Owolabi, Mayowa O; Ogun, Olufunmilola; Adeyinka, Abiodun; Ogunniyi, Adesola

    2015-01-01

    A variety of imaging modalities exist for the diagnosis of stroke. Several studies have been carried out to ascertain their contribution to the management of acute stroke and to compare the benefits and limitations of each modality. Diffusion-weighted imaging (DWI) has been described as the optimal imaging technique for diagnosing acute ischemic stroke, yet limited evidence is available on the value of DWI in the management of ischemic stroke with low-field magnetic resonance (MR) systems. Although high-field MR imaging (MRI) is desirable for DWI, low-field scanners provide an acceptable clinical compromise which is of importance to developing countries posed with the challenge of limited availability of high-field units. The purpose of this paper was to systematically review the literature on the usefulness of DWI in acute stroke management with low-field MRI scanners and present the experience in Nigeria. PMID:26709342

  8. Insights into the Performance Limits of the Li7P3S11 Superionic Conductor: A Combined First-Principles and Experimental Study.

    PubMed

    Chu, Iek-Heng; Nguyen, Han; Hy, Sunny; Lin, Yuh-Chieh; Wang, Zhenbin; Xu, Zihan; Deng, Zhi; Meng, Ying Shirley; Ong, Shyue Ping

    2016-03-01

    The Li7P3S11 glass-ceramic is a promising superionic conductor electrolyte (SCE) with an extremely high Li(+) conductivity that exceeds that of even traditional organic electrolytes. In this work, we present a combined computational and experimental investigation of the material performance limitations in terms of its phase and electrochemical stability, and Li(+) conductivity. We find that Li7P3S11 is metastable at 0 K but becomes stable at above 630 K (∼360 °C) when vibrational entropy contributions are accounted for, in agreement with differential scanning calorimetry measurements. Both scanning electron microscopy and the calculated Wulff shape show that Li7P3S11 tends to form relatively isotropic crystals. In terms of electrochemical stability, first-principles calculations predict that, unlike the LiCoO2 cathode, the olivine LiFePO4 and spinel LiMn2O4 cathodes are likely to form stable passivation interfaces with the Li7P3S11 SCE. This finding underscores the importance of considering multicomponent integration in developing an all-solid-state architecture. To probe the fundamental limit of its bulk Li(+) conductivity, a comparison of conventional cold-press sintered versus spark-plasma sintering (SPS) Li7P3S11 was done in conjunction with ab initio molecular dynamics (AIMD) simulations. Though the measured diffusion activation barriers are in excellent agreement, the AIMD-predicted room-temperature Li(+) conductivity of 57 mS cm(-1) is much higher than the experimental values. The optimized SPS sample exhibits a room-temperature Li(+) conductivity of 11.6 mS cm(-1), significantly higher than that of the cold-pressed sample (1.3 mS cm(-1)) due to the reduction of grain boundary resistance by densification. We conclude that grain boundary conductivity is limiting the overall Li(+) conductivity in Li7P3S11, and further optimization of overall conductivities should be possible. Finally, we show that Li(+) motions in this material are highly collective, and

  9. Reconstruction of limited-angle and few-view nano-CT image via total variation iterative reconstruction

    NASA Astrophysics Data System (ADS)

    Liang, Zhiting; Guan, Yong; Liu, Gang; Bian, Rui; Zhang, Xiaobo; Xiong, Ying; Tian, Yangchao

    2013-09-01

    Nano-CT has been considered as an important technique applied in analyzing inter-structures of nanomaterials and biological cell. However, maximum rotation angle of the sample stage is limited by sample space; meanwhile, the scan time is exorbitantly large to get enough projections in some cases. Therefore, it is difficult to acquire nano-CT images with high quality by using conventional Fourier reconstruction methods based on limited-angle or few-view projections. In this paper, we utilized the total variation (TV) iterative reconstruction to carry out numerical image and nano-CT image reconstruction with limited-angle and few-view data. The results indicated that better quality images had been achieved.

  10. Image-based surface reconstruction in geomorphometry - merits, limits and developments

    NASA Astrophysics Data System (ADS)

    Eltner, Anette; Kaiser, Andreas; Castillo, Carlos; Rock, Gilles; Neugirg, Fabian; Abellán, Antonio

    2016-05-01

    Photogrammetry and geosciences have been closely linked since the late 19th century due to the acquisition of high-quality 3-D data sets of the environment, but it has so far been restricted to a limited range of remote sensing specialists because of the considerable cost of metric systems for the acquisition and treatment of airborne imagery. Today, a wide range of commercial and open-source software tools enable the generation of 3-D and 4-D models of complex geomorphological features by geoscientists and other non-experts users. In addition, very recent rapid developments in unmanned aerial vehicle (UAV) technology allow for the flexible generation of high-quality aerial surveying and ortho-photography at a relatively low cost.The increasing computing capabilities during the last decade, together with the development of high-performance digital sensors and the important software innovations developed by computer-based vision and visual perception research fields, have extended the rigorous processing of stereoscopic image data to a 3-D point cloud generation from a series of non-calibrated images. Structure-from-motion (SfM) workflows are based upon algorithms for efficient and automatic orientation of large image sets without further data acquisition information, examples including robust feature detectors like the scale-invariant feature transform for 2-D imagery. Nevertheless, the importance of carrying out well-established fieldwork strategies, using proper camera settings, ground control points and ground truth for understanding the different sources of errors, still needs to be adapted in the common scientific practice.This review intends not only to summarise the current state of the art on using SfM workflows in geomorphometry but also to give an overview of terms and fields of application. Furthermore, this article aims to quantify already achieved accuracies and used scales, using different strategies in order to evaluate possible stagnations of

  11. Using Doppler shift induced by Galvanometric mirror scanning to reach shot noise limit with laser optical feedback imaging setup.

    PubMed

    Jacquin, O; Lacot, E; Hugon, O; Guillet de Chatelus, H

    2015-03-10

    This paper proposes what we believe is a new method to remove the contribution of parasitic reflections in the images of the laser optical feedback imaging (LOFI) technique. This simple method allows us to extend the LOFI technique to long-distance applications, as imaging through a fog or a smoke. The LOFI technique is an ultrasensitive imaging technique that is interesting for imaging objects through a scattering medium. However, the LOFI sensitivity can be dramatically limited by parasitic optical feedback occurring in the experimental setup. In previous papers [Appl. Opt.48, 64 (2009)10.1364/AO.48.000064APOPAI1559-128X, Opt. Lett.37, 2514 (2012)10.1364/OL.37.002514OPLEDP0146-9592], we already have proposed methods to filter a parasitic optical feedback, but they are not well suited to metric working distances. This new method uses a Doppler frequency shift induced by the moving mirror used to scan the object to be imaged. Using this Doppler frequency shift, we can distinguish the photons reflected by the target and the parasitic photons reflected by the optical components in the experimental setup. In this paper, we demonstrated theoretically and experimentally the possibility to filter the parasitic reflection in LOFI images using the Doppler frequency shift. This method significantly improves the signal-to-noise ratio by a factor 15 and we can obtain a shot noise limited image through a scattering medium of an object at 3 m from the detector. PMID:25968374

  12. Near-infrared InGaAs detectors for background-limited imaging and photometry

    NASA Astrophysics Data System (ADS)

    Sullivan, Peter W.; Croll, Bryce; Simcoe, Robert A.

    2014-07-01

    Originally designed for night-vision equipment, InGaAs detectors are beginning to achieve background-limited performance in broadband imaging from the ground. The lower cost of these detectors can enable multi-band instruments, arrays of small telescopes, and large focal planes that would be uneconomical with high-performance HgCdTe detectors. We developed a camera to operate the FLIR AP1121 sensor using deep thermoelectric cooling and up-the-ramp sampling to minimize noise. We measured a dark current of 163 e- s-1 pix-1, a read noise of 87 e- up-the-ramp, and a well depth of 80k e-. Laboratory photometric testing achieved a stability of 230 ppm hr-1/2, which would be required for detecting exoplanet transits. InGaAs detectors are also applicable to other branches of near-infrared time-domain astronomy, ranging from brown dwarf weather to gravitational wave follow-up.

  13. Uses, misuses, new uses and fundamental limitations of magnetic resonance imaging in cognitive science.

    PubMed

    Turner, Robert

    2016-10-01

    When blood oxygenation level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) was discovered in the early 1990s, it provoked an explosion of interest in exploring human cognition, using brain mapping techniques based on MRI. Standards for data acquisition and analysis were rapidly put in place, in order to assist comparison of results across laboratories. Recently, MRI data acquisition capabilities have improved dramatically, inviting a rethink of strategies for relating functional brain activity at the systems level with its neuronal substrates and functional connections. This paper reviews the established capabilities of BOLD contrast fMRI, the perceived weaknesses of major methods of analysis, and current results that may provide insights into improved brain modelling. These results have inspired the use of in vivo myeloarchitecture for localizing brain activity, individual subject analysis without spatial smoothing and mapping of changes in cerebral blood volume instead of BOLD activation changes. The apparent fundamental limitations of all methods based on nuclear magnetic resonance are also discussed.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'. PMID:27574303

  14. Bernoulli's Principle

    ERIC Educational Resources Information Center

    Hewitt, Paul G.

    2004-01-01

    Some teachers have difficulty understanding Bernoulli's principle particularly when the principle is applied to the aerodynamic lift. Some teachers favor using Newton's laws instead of Bernoulli's principle to explain the physics behind lift. Some also consider Bernoulli's principle too difficult to explain to students and avoid teaching it…

  15. Breaking the acoustic diffraction limit via nonlinear effect and thermal confinement for potential deep-tissue high-resolution imaging

    PubMed Central

    Yuan, Baohong; Pei, Yanbo; Kandukuri, Jayanth

    2013-01-01

    Our recently developed ultrasound-switchable fluorescence (USF) imaging technique showed that it was feasible to conduct high-resolution fluorescence imaging in a centimeter-deep turbid medium. Because the spatial resolution of this technique highly depends on the ultrasound-induced temperature focal size (UTFS), minimization of UTFS becomes important for further improving the spatial resolution USF technique. In this study, we found that UTFS can be significantly reduced below the diffraction-limited acoustic intensity focal size via nonlinear acoustic effects and thermal confinement by appropriately controlling ultrasound power and exposure time, which can be potentially used for deep-tissue high-resolution imaging. PMID:23479498

  16. A new VLA/e-MERLIN limit on central images in the gravitational lens system CLASS B1030+074

    NASA Astrophysics Data System (ADS)

    Quinn, Jonathan; Jackson, Neal; Tagore, Amitpal; Biggs, Andrew; Birkinshaw, Mark; Chapman, Scott; De Zotti, Gianfranco; McKean, John; Pérez-Fournon, Ismael; Scott, Douglas; Serjeant, Stephen

    2016-07-01

    We present the new Very Large Array 22 GHz and extended Multi-Element Remote-Linked Interferometer Network 5 GHz observations of CLASS B1030+074, a two-image strong gravitational lens system whose background source is a compact flat-spectrum radio quasar. In such systems we expect a third image of the background source to form close to the centre of the lensing galaxy. The existence and brightness of such images is important for investigation of the central mass distributions of lensing galaxies, but only one secure detection has been made so far in a galaxy-scale lens system. The noise levels achieved in our new B1030+074 images reach 3 μJy beam-1 and represent an improvement in central image constraints of nearly an order of magnitude over previous work, with correspondingly better resulting limits on the shape of the central mass profile of the lensing galaxy. Simple models with an isothermal outer power-law slope now require either the influence of a central supermassive black hole (SMBH), or an inner power-law slope very close to isothermal, in order to suppress the central image below our detection limit. Using the central mass profiles inferred from light distributions in Virgo galaxies, moved to z = 0.5, and matching to the observed Einstein radius, we now find that 45 per cent of such mass profiles should give observable central images, 10 per cent should give central images with a flux density still below our limit, and the remaining systems have extreme demagnification produced by the central SMBH. Further observations of similar objects will therefore allow proper statistical constraints to be placed on the central properties of elliptical galaxies at high redshift.

  17. Osteosarcoma Microenvironment: Whole-Slide Imaging and Optimized Antigen Detection Overcome Major Limitations in Immunohistochemical Quantification

    PubMed Central

    Kunz, Pierre; Fellenberg, Jörg; Moskovszky, Linda; Sápi, Zoltan; Krenacs, Tibor; Poeschl, Johannes; Lehner, Burkhard; Szendrõi, Miklos; Ewerbeck, Volker; Kinscherf, Ralf; Fritzsching, Benedikt

    2014-01-01

    applicable in decalcified formalin-fixed and paraffin-embedded samples for major parameters of the immunovascular microenvironment in osteosarcoma. Whole-slide imaging and optimized antigen retrieval overcome these limitations. PMID:24594971

  18. Non-rigid registration and non-local principle component analysis to improve electron microscopy spectrum images

    NASA Astrophysics Data System (ADS)

    Yankovich, Andrew B.; Zhang, Chenyu; Oh, Albert; Slater, Thomas J. A.; Azough, Feridoon; Freer, Robert; Haigh, Sarah J.; Willett, Rebecca; Voyles, Paul M.

    2016-09-01

    Image registration and non-local Poisson principal component analysis (PCA) denoising improve the quality of characteristic x-ray (EDS) spectrum imaging of Ca-stabilized Nd2/3TiO3 acquired at atomic resolution in a scanning transmission electron microscope. Image registration based on the simultaneously acquired high angle annular dark field image significantly outperforms acquisition with a long pixel dwell time or drift correction using a reference image. Non-local Poisson PCA denoising reduces noise more strongly than conventional weighted PCA while preserving atomic structure more faithfully. The reliability of and optimal internal parameters for non-local Poisson PCA denoising of EDS spectrum images is assessed using tests on phantom data.

  19. Fundamental limitations of reciprocal path imaging through the atmosphere with dilute subaperture arrays

    SciTech Connect

    Harvey, J.E.; Kotha, A.; Phillips, R.L.

    1994-12-31

    When synthesizing a large aperture with an array of smaller subapertures for high resolution imaging applications, it is important not only to arrange the subapertures to achieve minimal spatial frequency redundancy, but also to choose the size of the subapertures necessary to achieve the best possible image quality. Spurious or ``ghost`` images often occur even for non-redundant dilute subaperture arrays. In this paper the authors show that array configurations producing a uniform modulation transfer function will not exhibit these undesirable ghost images. A method is then presented for constructing both one-dimensional and two-dimensional configurations of dilute subaperture arrays that result in uniform spatial frequency response with arbitrarily high spatial resolution for reciprocal path imaging applications (i.e., imaging laser radar applications).

  20. Reaching the Diffraction Limit - Differential Speckle and Wide-Field Imaging for the Gemini-N Telescope

    NASA Technical Reports Server (NTRS)

    Scott, Nic J.; Howell, Steve; Horch, Elliott

    2016-01-01

    Speckle imaging allows telescopes to achieve di raction limited imaging performance. The technique requires cameras capable of reading out frames at a very fast rate, e ectively `freezing out' atmospheric seeing. The resulting speckles can be correlated and images reconstructed that are at the di raction limit of the telescope. These new instruments are based on the successful performance and design of the Di erential Speckle Survey Instrument (DSSI) [2, 1]. The instruments are being built for the Gemini-N and WIYN telescopes and will be made available to the community via the peer review proposal process. We envision their primary use to be validation and characterization of exoplanet targets from the NASA K2 and TESS missions and RV discovered exoplanets. Such targets will provide excellent follow-up candidates for both the WIYN and Gemini telescopes [3]. Examples of DSSI data are shown in the gures below. We expect similar data quality in speckle imaging mode with the new instruments. Additionally, both cameras will have a wide- eld mode and standard SDSS lters. They will be highly versatile instruments and it is that likely many other science programs will request time on the cameras. The limiting magnitude for speckle observations, will remain around 13-14th at WIYN and 16-17th at Gemini, while wide- eld, normal CCD imaging operation should be able to go to much fainter, providing usual CCD imaging and photometric capabilities. The instruments will also have high utility as scoring cameras for telescope engineering purposes, or other applications where high time resolution is needed. Instrument support will be provided, including a software pipeline that takes raw speckle data to fully reconstructed images.

  1. Image Maps in the World-Wide Web: The Uses and Limitations.

    ERIC Educational Resources Information Center

    Cochenour, John J.; And Others

    A study of nine different image maps from World Wide Web home pages was conducted to evaluate their effectiveness in information display and access, relative to visual, navigational, and practical characteristics. Nine independent viewers completed 20-question surveys on the image maps, in which they evaluated the characteristics of the maps on a…

  2. Magnetic Resonance Imaging of Bilirubin Encephalopathy: Current Limitations and Future Promise

    PubMed Central

    Wisnowski, Jessica L.; Panigrahy, Ashok; Painter, Michael J.; Watchko, Jon F.

    2014-01-01

    Infants with chronic bilirubin encephalopathy often demonstrate abnormal bilateral, symmetric, high-signal intensity on T2-weighted magnetic resonance imaging of the globus pallidus and subthalamic nucleus, consistent with the neuropathology of kernicterus. Early magnetic resonance imaging of at risk infants, while frequently showing increased T1-signal in these regions, may give false positive findings due to the presence of myelin in these structures. Advanced magnetic resonance imaging including diffusion-weighted imaging, magnetic resonance spectroscopy, and diffusion tensor imaging with tractography may shed new insights into the pathogenesis of bilirubin-induced brain injury and the neural basis of long-term disability in infants and children with chronic bilirubin encephalopathy. PMID:25267277

  3. Depth of field of diffraction-limited imaging system incorporating electronic devices

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kimiaki

    2014-11-01

    The depth of field is investigated for an imaging system in which optical imaging and electronic devices, such as an electronic sensor and a display, are combined. When the spatial frequency of pixels in the electronic devices is higher than the cut-off frequency of the optical system, it is shown that the depth of field is almost the same as that of the optical system itself. In the case where the spatial frequency is lower than the cut-off frequency of the optical system, the depth of field increases, and the features of the increase are shown in imaging systems both with and without an optical low-pass filter.

  4. Pitfalls and Limitations of Diffusion-Weighted Magnetic Resonance Imaging in the Diagnosis of Urinary Bladder Cancer

    PubMed Central

    Lin, Wei-Ching; Chen, Jeon-Hor

    2015-01-01

    Adequately selecting a therapeutic approach for bladder cancer depends on accurate grading and staging. Substantial inaccuracy of clinical staging with bimanual examination, cystoscopy, and transurethral resection of bladder tumor has facilitated the increasing utility of magnetic resonance imaging to evaluate bladder cancer. Diffusion-weighted imaging (DWI) is a noninvasive functional magnetic resonance imaging technique. The high tissue contrast between cancers and surrounding tissues on DWI is derived from the difference of water molecules motion. DWI is potentially a useful tool for the detection, characterization, and staging of bladder cancers; it can also monitor posttreatment response and provide information on predicting tumor biophysical behaviors. Despite advancements in DWI techniques and the use of quantitative analysis to evaluate the apparent diffusion coefficient values, there are some inherent limitations in DWI interpretation related to relatively poor spatial resolution, lack of cancer specificity, and lack of standardized image acquisition protocols and data analysis procedures that restrict the application of DWI and reproducibility of apparent diffusion coefficient values. In addition, inadequate bladder distension, artifacts, thinness of bladder wall, cancerous mimickers of normal bladder wall and benign lesions, and variations in the manifestation of bladder cancer may interfere with diagnosis and monitoring of treatment. Recognition of these pitfalls and limitations can minimize their impact on image interpretation, and carefully applying the analyzed results and combining with pathologic grading and staging to clinical practice can contribute to the selection of an adequate treatment method to improve patient care. PMID:26055180

  5. Distortion-free magnetic resonance imaging in the zero-field limit

    SciTech Connect

    Kelso, Nathan; Lee, Seung-Kyun; Bouchard, Louis-S.; Demas, Vasiliki; Muck, Michael; Pines, Alexander; Clarke, John

    2009-07-09

    MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell's equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth's field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions.

  6. [Exchange of medical imaging and data information in radiotherapy: needs, methods and current limits].

    PubMed

    Manens, J P

    1997-01-01

    Extension of the image network within radiotherapy departments provides the technical infrastructure which is made necessary by the rapid evolution of techniques in the field of diagnosis and treatment in radiotherapy. The system is aimed at managing the whole set of data (textual data and images) that are needed for planning and control of treatments. The radiotherapy network addresses two objectives: managing both the information necessary for treatment planning (target volumes definition, planning dosimetry) and the control of all parameters involved during the patient's treatment under the treatment unit. The major challenge is to improve the quality of treatment. Multimodal imaging is a major advance as it allows the use of new dosimetry and simulation techniques. The need for standards to exchange medical imaging information is now recognized by all the institutions and a majority of users and manufacturers. It is widely accepted that the lack of standard has been one of the fundamental obstacles in the deployment of operational "Picture Archiving Communication Systems". The International Standard Organisation Open System Interconnection model is the standard reference mode used to describe network protocols. The network is based on the Ethernet and TCP/IP protocol that provides the means to interconnect imaging devices and workstations dedicated to specific image processing or machines used in radiotherapy. The network uses Ethernet cabled on twisted-pair (10 BaseT) or optical fibres in a star-shaped physical layout. Dicom V3.0 supports fundamental network interactions: transfer of images (computerized tomography magnetic resonance imaging query and retrieve of images), printing on network attached cameras, support of HIS/RIS related interfacing and image management. The supplement to the Dicom standard, Dicom RT, specifies five data objects known in Dicom as Information Object Definition for relevant radiotherapy. Dicom RT objects can provide a mean for

  7. Imaging with depth extension: where are the limits in fixed- focus cameras?

    NASA Astrophysics Data System (ADS)

    Bakin, Dmitry; Keelan, Brian

    2008-08-01

    The integration of novel optics designs, miniature CMOS sensors, and powerful digital processing into a single imaging module package is driving progress in handset camera systems in terms of performance, size (thinness) and cost. The miniature cameras incorporating high resolution sensors and fixed-focus Extended Depth of Field (EDOF) optics allow close-range reading of printed material (barcode patterns, business cards), while providing high quality imaging in more traditional applications. These cameras incorporate modified optics and digital processing to recover the soft-focus images and restore sharpness over a wide range of object distances. The effects a variety of parameters of the imaging module on the EDOF range were analyzed for a family of high resolution CMOS modules. The parameters include various optical properties of the imaging lens, and the characteristics of the sensor. The extension factors for the EDOF imaging module were defined in terms of an improved absolute resolution in object space while maintaining focus at infinity. This definition was applied for the purpose of identifying the minimally resolvable object details in mobile cameras with bar-code reading feature.

  8. 3D face reconstruction from limited images based on differential evolution

    NASA Astrophysics Data System (ADS)

    Wang, Qun; Li, Jiang; Asari, Vijayan K.; Karim, Mohammad A.

    2011-09-01

    3D face modeling has been one of the greatest challenges for researchers in computer graphics for many years. Various methods have been used to model the shape and texture of faces under varying illumination and pose conditions from a single given image. In this paper, we propose a novel method for the 3D face synthesis and reconstruction by using a simple and efficient global optimizer. A 3D-2D matching algorithm which employs the integration of the 3D morphable model (3DMM) and the differential evolution (DE) algorithm is addressed. In 3DMM, the estimation process of fitting shape and texture information into 2D images is considered as the problem of searching for the global minimum in a high dimensional feature space, in which optimization is apt to have local convergence. Unlike the traditional scheme used in 3DMM, DE appears to be robust against stagnation in local minima and sensitiveness to initial values in face reconstruction. Benefitting from DE's successful performance, 3D face models can be created based on a single 2D image with respect to various illuminating and pose contexts. Preliminary results demonstrate that we are able to automatically create a virtual 3D face from a single 2D image with high performance. The validation process shows that there is only an insignificant difference between the input image and the 2D face image projected by the 3D model.

  9. Surface roughness limited contrast to clutter ratios THz medical imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sung, Shijun; Bajwa, Neha; Goell, Jacob; Taylor, Zachary

    2016-03-01

    The THz electromagnetic properties of rough surface are explored and their effect on the observed contrast in THz images is quantified. Rough surface scatter is a major source of clutter in THz imaging as the rough features of skin and other tissues result in non-trivial reflection signal modulation. Traditional approaches to data collection utilize dielectric windows to flatten surfaces for THz imaging. However, there is substantial interest surrounding window free imaging as contact measurements are not ideal for a range of candidate diseases and injuries. In this work we investigate the variation in reflected signal in the specular direction from rough surfaces targets with known roughness parameters. Signal to clutter ratios are computed and compared with that predicted by Rayleigh Rough surface scattering theory. It is shown that Rayleigh rough surface scattering theory, developed for rough features larger than the interacting wavelength, holds acceptable at THz frequencies with rough features much smaller than the wavelength. Additionally, we present some biological tissue imaging examples to illustrate the impact of rough surface scattering in image quality.

  10. K{sub α} x-ray imaging of laser-irradiated, limited-mass zirconium foils

    SciTech Connect

    Storm, M.; Orban, C.; Jiang, S.; Freeman, R. R.; Akli, K.; Eichman, B.; Fiksel, G.; Stoeckl, C.; Theobald, W.; Delettrez, J. A.; Dyer, G.; Ditmire, T.; Stephens, R.

    2014-07-15

    X-ray fluorescence measurements to determine the effect of target heating on imaging efficiency, at a photon energy of 15.7 keV corresponding to the K{sub α} line of zirconium, have been carried out using limited-mass foils irradiated by the Texas Petawatt Laser. Zirconium foils that ranged in volume from 3000 × 3000 × 21 μm{sup 3} to 150 × 150 × 6 μm{sup 3} were irradiated with 100 J, 8 ps-long pulses and a mean intensity of 4 × 10{sup 19} W/cm{sup 2}. The K{sub α} emission was measured simultaneously using a highly ordered pyrolytic graphite crystal spectrometer and a curved quartz imaging crystal. The measured ratio of the integrated image signal to the integrated spectral signal was, within the experimental error, constant, indicating that the imaging efficiency's dependence on temperature is weak throughout the probed range. Based on our experience of target heating under similar conditions, we estimate a temperature of ∼200 eV for the smallest targets. The successful imaging of K{sub α} emission for temperatures this high represents an important proof of concept for Zr K{sub α} imaging. At these temperatures, the imaging of K{sub α} emission from lower-Z materials (such as Cu) is limited by temperature-dependent shifts in the K{sub α} emission energy.

  11. Improved estimation of parametric images of cerebral glucose metabolic rate from dynamic FDG-PET using volume-wise principle component analysis

    NASA Astrophysics Data System (ADS)

    Dai, Xiaoqian; Tian, Jie; Chen, Zhe

    2010-03-01

    Parametric images can represent both spatial distribution and quantification of the biological and physiological parameters of tracer kinetics. The linear least square (LLS) method is a well-estimated linear regression method for generating parametric images by fitting compartment models with good computational efficiency. However, bias exists in LLS-based parameter estimates, owing to the noise present in tissue time activity curves (TTACs) that propagates as correlated error in the LLS linearized equations. To address this problem, a volume-wise principal component analysis (PCA) based method is proposed. In this method, firstly dynamic PET data are properly pre-transformed to standardize noise variance as PCA is a data driven technique and can not itself separate signals from noise. Secondly, the volume-wise PCA is applied on PET data. The signals can be mostly represented by the first few principle components (PC) and the noise is left in the subsequent PCs. Then the noise-reduced data are obtained using the first few PCs by applying 'inverse PCA'. It should also be transformed back according to the pre-transformation method used in the first step to maintain the scale of the original data set. Finally, the obtained new data set is used to generate parametric images using the linear least squares (LLS) estimation method. Compared with other noise-removal method, the proposed method can achieve high statistical reliability in the generated parametric images. The effectiveness of the method is demonstrated both with computer simulation and with clinical dynamic FDG PET study.

  12. Using Principles of Programmed Instruction

    ERIC Educational Resources Information Center

    Huffman, Harry

    1971-01-01

    Although programmed instruction in accounting is available, it is limited in scope and in acceptance. Teachers, however, may apply principles of programming to the individualizing of instruction. (Author)

  13. Accounting for Variance in Hyperspectral Data Coming from Limitations of the Imaging System

    NASA Astrophysics Data System (ADS)

    Shurygin, B.; Shestakova, M.; Nikolenko, A.; Badasen, E.; Strakhov, P.

    2016-06-01

    Over the course of the past few years, a number of methods was developed to incorporate hyperspectral imaging specifics into generic data mining techniques, traditionally used for hyperspectral data processing. Projection pursuit methods embody the largest class of methods empoyed for hyperspectral image data reduction, however, they all have certain drawbacks making them either hard to use or inefficient. It has been shown that hyperspectral image (HSI) statistics tend to display "heavy tails" (Manolakis2003)(Theiler2005), rendering most of the projection pursuit methods hard to use. Taking into consideration the magnitude of described deviations of observed data PDFs from normal distribution, it is apparent that a priori knowledge of variance in data caused by the imaging system is to be employed in order to efficiently classify objects on HSIs (Kerr, 2015), especially in cases of wildly varying SNR. A number of attempts to describe this variance and compensating techniques has been made (Aiazzi2006), however, new data quality standards are not yet set and accounting for the detector response is made under large set of assumptions. Current paper addresses the issue of hyperspectral image classification in the context of different variance sources based on the knowledge of calibration curves (both spectral and radiometric) obtained for each pixel of imaging camera. A camera produced by ZAO NPO Lepton (Russia) was calibrated and used to obtain a test image. A priori known values of SNR and spectral channel cross-correlation were incorporated into calculating test statistics used in dimensionality reduction and feature extraction. Expectation-Maximization classification algorithm modification for non-Gaussian model as described by (Veracini2010) was further employed. The impact of calibration data coarsening by ignoring non-uniformities on false alarm rate was studied. Case study shows both regions of scene-dominated variance and sensor-dominated variance, leading

  14. Fifty Years of Technological Innovation: Potential and Limitations of Current Technologies in Abdominal Magnetic Resonance Imaging and Computed Tomography.

    PubMed

    Attenberger, Ulrike I; Morelli, John; Budjan, Johannes; Henzler, Thomas; Sourbron, Steven; Bock, Michael; Riffel, Philipp; Hernando, Diego; Ong, Melissa M; Schoenberg, Stefan O

    2015-09-01

    Magnetic resonance imaging (MRI) has become an important modality for the diagnosis of intra-abdominal pathology. Hardware and pulse sequence developments have made it possible to derive not only morphologic but also functional information related to organ perfusion (dynamic contrast-enhanced MRI), oxygen saturation (blood oxygen level dependent), tissue cellularity (diffusion-weighted imaging), and tissue composition (spectroscopy). These techniques enable a more specific assessment of pathologic lesions and organ functionality. Magnetic resonance imaging has thus transitioned from a purely morphologic examination to a modality from which image-based disease biomarkers can be derived. This fits well with several emerging trends in radiology, such as the need to accurately assess response to costly treatment strategies and the need to improve lesion characterization to potentially avoid biopsy. Meanwhile, the cost-effectiveness, availability, and robustness of computed tomography (CT) ensure its place as the current workhorse for clinical imaging. Although the lower soft tissue contrast of CT relative to MRI is a long-standing limitation, other disadvantages such as ionizing radiation exposure have become a matter of public concern. Nevertheless, recent technical developments such as dual-energy CT or dynamic volume perfusion CT also provide more functional imaging beyond morphology.The aim of this article was to review and discuss the most important recent technical developments in abdominal MRI and state-of-the-art CT, with an eye toward the future, providing examples of their clinical utility for the evaluation of hepatic and renal pathologies. PMID:26039773

  15. Multimode C-arm fluoroscopy, tomosynthesis, and cone-beam CT for image-guided interventions: from proof of principle to patient protocols

    NASA Astrophysics Data System (ADS)

    Siewerdsen, J. H.; Daly, M. J.; Bachar, G.; Moseley, D. J.; Bootsma, G.; Brock, K. K.; Ansell, S.; Wilson, G. A.; Chhabra, S.; Jaffray, D. A.; Irish, J. C.

    2007-03-01

    High-performance intraoperative imaging is essential to an ever-expanding scope of therapeutic procedures ranging from tumor surgery to interventional radiology. The need for precise visualization of bony and soft-tissue structures with minimal obstruction to the therapy setup presents challenges and opportunities in the development of novel imaging technologies specifically for image-guided procedures. Over the past ~5 years, a mobile C-arm has been modified in collaboration with Siemens Medical Solutions for 3D imaging. Based upon a Siemens PowerMobil, the device includes: a flat-panel detector (Varian PaxScan 4030CB); a motorized orbit; a system for geometric calibration; integration with real-time tracking and navigation (NDI Polaris); and a computer control system for multi-mode fluoroscopy, tomosynthesis, and cone-beam CT. Investigation of 3D imaging performance (noise-equivalent quanta), image quality (human observer studies), and image artifacts (scatter, truncation, and cone-beam artifacts) has driven the development of imaging techniques appropriate to a host of image-guided interventions. Multi-mode functionality presents a valuable spectrum of acquisition techniques: i.) fluoroscopy for real-time 2D guidance; ii.) limited-angle tomosynthesis for fast 3D imaging (e.g., ~10 sec acquisition of coronal slices containing the surgical target); and iii.) fully 3D cone-beam CT (e.g., ~30-60 sec acquisition providing bony and soft-tissue visualization across the field of view). Phantom and cadaver studies clearly indicate the potential for improved surgical performance - up to a factor of 2 increase in challenging surgical target excisions. The C-arm system is currently being deployed in patient protocols ranging from brachytherapy to chest, breast, spine, and head and neck surgery.

  16. Limits of Active Laser Triangulation as an Instrument for High Precision Plant Imaging

    PubMed Central

    Paulus, Stefan; Eichert, Thomas; Goldbach, Heiner E.; Kuhlmann, Heiner

    2014-01-01

    Laser scanning is a non-invasive method for collecting and parameterizing 3D data of well reflecting objects. These systems have been used for 3D imaging of plant growth and structure analysis. A prerequisite is that the recorded signals originate from the true plant surface. In this paper we studied the effects of species, leaf chlorophyll content and sensor settings on the suitability and accuracy of a commercial 660 nm active laser triangulation scanning device. We found that surface images of Ficus benjamina leaves were inaccurate at low chlorophyll concentrations and a long sensor exposure time. Imaging of the rough waxy leaf surface of leek (Allium porrum) was possible using very low exposure times, whereas at higher exposure times penetration and multiple refraction prevented the correct imaging of the surface. A comparison of scans with varying exposure time enabled the target-oriented analysis to identify chlorotic, necrotic and healthy leaf areas or mildew infestations. We found plant properties and sensor settings to have a strong influence on the accuracy of measurements. These interactions have to be further elucidated before laser imaging of plants is possible with the high accuracy required for e.g., the observation of plant growth or reactions to water stress. PMID:24504106

  17. Data reduction pipeline for OSIRIS, the new NIR diffraction-limited imaging field spectrograph for the Keck adaptive optics system

    NASA Astrophysics Data System (ADS)

    Krabbe, Alfred; Gasaway, Tom; Song, Inseok; Iserlohe, Christof; Weiss, Jason; Larkin, James E.; Barczys, Matthew; Lafreniere, David

    2004-09-01

    OSIRIS is a near infrared diffraction limited imaging field spectrograph under development for the Keck observatory adaptive optics system and scheduled for commissioning in fall 2004. Based upon lenslet pupil imaging, diffraction grating, and a 2Kx2K Hawaii2 HgCdTe array, OSIRIS is a highly efficient instrument at the forefront of today's technology. OSIRIS will deliver per readout up to 4096 diffraction limited spectra in a complex interleaved format, requiring new challenges to be met regarding user interaction and data reduction. A data reduction software package is under development, aiming to provide the observer with a facility instrument allowing him to concentrate on science rather than dealing with instrumental as well as telescope and atmosphere related effects. Together with OSIRIS, a pipeline for basic data reduction will be provided for a new Keck instrument for the first time. A status report is presented here together with some aspects of the data reduction pipeline.

  18. The Magellan Adaptive Secondary VisAO Camera: diffraction-limited broadband visible imaging and 20mas fiber array IFU

    NASA Astrophysics Data System (ADS)

    Kopon, Derek; Close, Laird M.; Males, Jared; Gasho, Victor; Follette, Katherine

    2010-07-01

    The Magellan Adaptive Secondary AO system, scheduled for first light in the fall of 2011, will be able to simultaneously perform diffraction limited AO science in both the mid-IR, using the BLINC/MIRAC4 10μm camera, and in the visible using our novel VisAO camera. The VisAO camera will be able to operate as either an imager, using a CCD47 with 8.5 mas pixels, or as an IFS, using a custom fiber array at the focal plane with 20 mas elements in its highest resolution mode. In imaging mode, the VisAO camera will have a full suite of filters, coronagraphic focal plane occulting spots, and SDI prism/filters. The imaging mode should provide ~20% mean Strehl diffraction-limited images over the band 0.5-1.0 μm. In IFS mode, the VisAO instrument will provide R~1,800 spectra over the band 0.6-1.05 μm. Our unprecedented 20 mas spatially resolved visible spectra would be the highest spatial resolution achieved to date, either from the ground or in space. We also present lab results from our recently fabricated advanced triplet Atmospheric Dispersion Corrector (ADC) and the design of our novel wide-field acquisition and active optics lens. The advanced ADC is designed to perform 58% better than conventional doublet ADCs and is one of the enabling technologies that will allow us to achieve broadband (0.5-1.0μm) diffraction limited imaging and wavefront sensing in the visible.

  19. Computed Tomography Image Compressibility and Limitations of Compression Ratio-Based Guidelines.

    PubMed

    Pambrun, Jean-François; Noumeir, Rita

    2015-12-01

    Finding optimal compression levels for diagnostic imaging is not an easy task. Significant compressibility variations exist between modalities, but little is known about compressibility variations within modalities. Moreover, compressibility is affected by acquisition parameters. In this study, we evaluate the compressibility of thousands of computed tomography (CT) slices acquired with different slice thicknesses, exposures, reconstruction filters, slice collimations, and pitches. We demonstrate that exposure, slice thickness, and reconstruction filters have a significant impact on image compressibility due to an increased high frequency content and a lower acquisition signal-to-noise ratio. We also show that compression ratio is not a good fidelity measure. Therefore, guidelines based on compression ratio should ideally be replaced with other compression measures better correlated with image fidelity. Value-of-interest (VOI) transformations also affect the perception of quality. We have studied the effect of value-of-interest transformation and found significant masking of artifacts when window is widened. PMID:25804842

  20. An Empirical Model of Body Image Disturbance Using Behavioral Principles Found in Functional Analytic Psychotherapy and Acceptance and Commitment Therapy

    ERIC Educational Resources Information Center

    Callaghan, Glenn M.; Duenas, Julissa A.; Nadeau, Sarah E.; Darrow, Sabrina M.; Van der Merwe, Jessica; Misko, Jennifer

    2012-01-01

    The literature examining body image disturbance and Body Dysmorphic Disorder (BDD) is fraught with competing theoretical constructions of the etiology and nosology of these problems. Recent studies on various forms of psychopathology suggest that intrapersonal processes, including experiential avoidance, and interpersonal processes such as…

  1. Apparent limitations of head-up-displays and thermal imaging systems

    NASA Technical Reports Server (NTRS)

    Brickner, Michael S.

    1989-01-01

    A simulated helicopter flight through a slalom course was presented on a Silicon Graphics IRIS 3130. The display represented the major visual characteristics of thermal images. Subjects were asked to maintain a designated altitude, while flying a slalom course between regularly spaced pylons. The presence of some of the high frequency details in the image improved subjects' ability to reach and maintain the correct altitude. A head-up-display helped in maintaining altitude, but impaired maneuvering around the poles. The results are interpreted in terms of the competition for visual resources between the HUD and the world view.

  2. Benefits and Limitations of Low-kV Macromolecular Imaging of Frozen-Hydrated Biological Samples.

    PubMed

    Majorovits, Endre; Angert, Isabel; Kaiser, Ute; Schröder, Rasmus R

    2016-02-23

    Object contrast is one of the most important parameters of macromolecular imaging. Low-voltage transmission electron microscopy has shown an increased atom contrast for carbon materials, indicating that amplitude contrast contributions increase at a higher rate than phase contrast and inelastic scattering. Here, we studied image contrast using ice-embedded tobacco mosaic virus particles as test samples at 20-80 keV electron energy. The particles showed the expected increase in contrast for lower energies, but at the same time the 2.3-nm-resolution measure decayed more rapidly. We found a pronounced signal loss below 60 keV, and therefore we conclude that increased inelastic scattering counteracts increased amplitude contrast. This model also implies that as long as the amplitude contrast does not increase with resolution, beam damage and multiple scattering will always win over increased contrast at the lowest energies. Therefore, we cannot expect that low-energy imaging of conventionally prepared samples would provide better data than state-of-the-art 200-300 keV imaging. PMID:26910420

  3. Some Remarks on Imaging of the Inner Ear: Options and Limitations.

    PubMed

    Giesemann, A; Hofmann, E

    2015-10-01

    The temporal bone has a highly complex anatomical structure, in which the sensory organs of the cochlea and the vestibular system are contained within a small space together with the sound-conducting system of the middle ear. Detailed imaging is thus required in this anatomical area. There are a great many clinical aims for which the highest-possible spatial resolution is required. These include the localization of cerebrospinal fluid fistulas, the detection of malformations of the middle and inner ear and the vestibulocochlear nerve, an aberrant course of the facial nerve and anomalies of the arterial and venous structures, the confirmation of dehiscence of the semicircular canals and finally, the verification of endolymphatic hydrops in cases of Ménière's disease. However, the term 'high resolution' is very time dependent. Two milestones in this respect have been (in 1991) the 3D visualization of the inner ear by means of maximum-intensity projection (MIP) of a T2-weighted constructive interference in steady state (CISS) sequence of a 1.5-tesla magnetic resonance imaging (MRI) scanner (Tanioka et al., Radiology 178:141-144, 1991) and (in 1997) imaging of the vestibulocochlear nerve for the diagnosis of hypoplasia inside the internal auditory canal using the same sequence (Casselman et al., Radiology 202:773-781, 1997).The objective of this article is to highlight the options for, and the challenges of, contemporary imaging with regard to some clinical issues relating to the inner ear. PMID:26153464

  4. Pre-processing SAR image stream to facilitate compression for transport on bandwidth-limited-link

    SciTech Connect

    Rush, Bobby G.; Riley, Robert

    2015-09-29

    Pre-processing is applied to a raw VideoSAR (or similar near-video rate) product to transform the image frame sequence into a product that resembles more closely the type of product for which conventional video codecs are designed, while sufficiently maintaining utility and visual quality of the product delivered by the codec.

  5. Visual Links in the World-Wide Web: The Uses and Limitations of Image Maps.

    ERIC Educational Resources Information Center

    Cochenour, John J.; And Others

    As information delivery systems on the Internet increasingly evolve into World Wide Web browsers, understanding key graphical elements of the browser interface is critical to the design of effective information display and access tools. Image maps are one such element, and this document describes a pilot study that collected, reviewed, and…

  6. Dynamic sealing principles

    NASA Technical Reports Server (NTRS)

    Zuk, J.

    1976-01-01

    The fundamental principles governing dynamic sealing operation are discussed. Different seals are described in terms of these principles. Despite the large variety of detailed construction, there appear to be some basic principles, or combinations of basic principles, by which all seals function, these are presented and discussed. Theoretical and practical considerations in the application of these principles are discussed. Advantages, disadvantages, limitations, and application examples of various conventional and special seals are presented. Fundamental equations governing liquid and gas flows in thin film seals, which enable leakage calculations to be made, are also presented. Concept of flow functions, application of Reynolds lubrication equation, and nonlubrication equation flow, friction and wear; and seal lubrication regimes are explained.

  7. INTRAOPERATIVE SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING AFTER INTERNAL LIMITING MEMBRANE PEELING IN IDIOPATHIC EPIRETINAL MEMBRANE WITH CONNECTING STRANDS

    PubMed Central

    NAM, DONG HEUN; DESOUZA, PHILIP J.; HAHN, PAUL; TAI, VINCENT; SEVILLA, MONICA B.; TRAN-VIET, DU; CUNEFARE, DAVID; FARSIU, SINA; IZATT, JOSEPH A.; TOTH, CYNTHIA A.

    2015-01-01

    Purpose To report the intraoperative optical coherence tomography findings in idiopathic epiretinal membrane (ERM) with connecting strands and to describe the postoperative outcomes. Methods A retrospective, case series study within a prospective observational intraoperative optical coherence tomography imaging study was performed. Epiretinal membranes with connecting strands were characterized on preoperative spectral domain optical coherence tomography images and assessed against corresponding intraoperative (after internal limiting membrane [ILM] peeling) and postoperative spectral domain optical coherence tomography images. Results Eleven locations of the connecting strands in 7 eyes were studied. The connecting strands had visible connections from the inner retinal surface to the ERM in all locations, and the reflectivity was moderate in 8 locations and high in 3 locations. After ERM and ILM peeling, disconnected strands were identified in all of the intraoperative optical coherence tomography images. The reflectivity of the remaining intraoperative strands was higher than that of the preoperative lesions and appeared as “finger-like” and branching projections. The remaining disconnected lesions were contiguous with the inner retinal layers. Postoperatively, the intraoperative lesions disappeared completely in all locations, and recurrent formation of ERM was not identified in any eyes. Conclusion In ERM eyes with connecting strands, intraoperative spectral domain optical coherence tomography imaging showed moderately to highly reflective sub-ILM finger-like lesions that persist immediately after membrane and ILM peeling. Postoperatively, the hyperreflective lesions disappeared spontaneously without localized nerve fiber layer loss. The sub-ILM connecting strands may represent glial retinal attachments. PMID:25829349

  8. Enhancement of low-quality reconstructed digital hologram images based on frequency extrapolation of large objects under the diffraction limit

    NASA Astrophysics Data System (ADS)

    Liu, Ning; Li, Weiliang; Zhao, Dongxue

    2016-03-01

    During the reconstruction of a digital hologram, the reconstructed image is usually degraded by speckle noise, which makes it hard to observe the original object pattern. In this paper, a new reconstructed image enhancement method is proposed, which first reduces the speckle noise using an adaptive Gaussian filter, then calculates the high frequencies that belong to the object pattern based on a frequency extrapolation strategy. The proposed frequency extrapolation first calculates the frequency spectrum of the Fourier-filtered image, which is originally reconstructed from the +1 order of the hologram, and then gives the initial parameters for an iterative solution. The analytic iteration is implemented by continuous gradient threshold convergence to estimate the image level and vertical gradient information. The predicted spectrum is acquired through the analytical iteration of the original spectrum and gradient spectrum analysis. Finally, the reconstructed spectrum of the restoration image is acquired from the synthetic correction of the original spectrum using the predicted gradient spectrum. We conducted our experiment very close to the diffraction limit and used low-quality equipment to prove the feasibility of our method. Detailed analysis and figure demonstrations are presented in the paper.

  9. Enhancement of low-quality reconstructed digital hologram images based on frequency extrapolation of large objects under the diffraction limit

    NASA Astrophysics Data System (ADS)

    Liu, Ning; Li, Weiliang; Zhao, Dongxue

    2016-06-01

    During the reconstruction of a digital hologram, the reconstructed image is usually degraded by speckle noise, which makes it hard to observe the original object pattern. In this paper, a new reconstructed image enhancement method is proposed, which first reduces the speckle noise using an adaptive Gaussian filter, then calculates the high frequencies that belong to the object pattern based on a frequency extrapolation strategy. The proposed frequency extrapolation first calculates the frequency spectrum of the Fourier-filtered image, which is originally reconstructed from the +1 order of the hologram, and then gives the initial parameters for an iterative solution. The analytic iteration is implemented by continuous gradient threshold convergence to estimate the image level and vertical gradient information. The predicted spectrum is acquired through the analytical iteration of the original spectrum and gradient spectrum analysis. Finally, the reconstructed spectrum of the restoration image is acquired from the synthetic correction of the original spectrum using the predicted gradient spectrum. We conducted our experiment very close to the diffraction limit and used low-quality equipment to prove the feasibility of our method. Detailed analysis and figure demonstrations are presented in the paper.

  10. Buridan's Principle

    NASA Astrophysics Data System (ADS)

    Lamport, Leslie

    2012-08-01

    Buridan's principle asserts that a discrete decision based upon input having a continuous range of values cannot be made within a bounded length of time. It appears to be a fundamental law of nature. Engineers aware of it can design devices so they have an infinitessimal probability of not making a decision quickly enough. Ignorance of the principle could have serious consequences.

  11. Principled Narrative

    ERIC Educational Resources Information Center

    MacBeath, John; Swaffield, Sue; Frost, David

    2009-01-01

    This article provides an overview of the "Carpe Vitam: Leadership for Learning" project, accounting for its provenance and purposes, before focusing on the principles for practice that constitute an important part of the project's legacy. These principles framed the dialogic process that was a dominant feature of the project and are presented,…

  12. Breaking the limits of structural and mechanical imaging of the heterogeneous structure of coal macerals

    NASA Astrophysics Data System (ADS)

    Collins, L.; Tselev, A.; Jesse, S.; Okatan, M. B.; Proksch, R.; Mathews, J. P.; Mitchell, G. D.; Rodriguez, B. J.; Kalinin, S. V.; Ivanov, I. N.

    2014-10-01

    The correlation between local mechanical (elasto-plastic) and structural (composition) properties of coal presents significant fundamental and practical interest for coal processing and for the development of rheological models of coal to coke transformations. Here, we explore the relationship between the local structural, chemical composition, and mechanical properties of coal using a combination of confocal micro-Raman imaging and band excitation atomic force acoustic microscopy for a bituminous coal. This allows high resolution imaging (10s of nm) of mechanical properties of the heterogeneous (banded) architecture of coal and correlating them to the optical gap, average crystallite size, the bond-bending disorder of sp2 aromatic double bonds, and the defect density. This methodology allows the structural and mechanical properties of coal components (lithotypes, microlithotypes, and macerals) to be understood, and related to local chemical structure, potentially allowing for knowledge-based modeling and optimization of coal utilization processes.

  13. Breaking the limits of structural and mechanical imaging of the heterogeneous structure of coal macerals.

    PubMed

    Collins, L; Tselev, A; Jesse, S; Okatan, M B; Proksch, R; Mathews, J P; Mitchell, G D; Rodriguez, B J; Kalinin, S V; Ivanov, I N

    2014-10-31

    The correlation between local mechanical (elasto-plastic) and structural (composition) properties of coal presents significant fundamental and practical interest for coal processing and for the development of rheological models of coal to coke transformations. Here, we explore the relationship between the local structural, chemical composition, and mechanical properties of coal using a combination of confocal micro-Raman imaging and band excitation atomic force acoustic microscopy for a bituminous coal. This allows high resolution imaging (10s of nm) of mechanical properties of the heterogeneous (banded) architecture of coal and correlating them to the optical gap, average crystallite size, the bond-bending disorder of sp(2) aromatic double bonds, and the defect density. This methodology allows the structural and mechanical properties of coal components (lithotypes, microlithotypes, and macerals) to be understood, and related to local chemical structure, potentially allowing for knowledge-based modeling and optimization of coal utilization processes. PMID:25299223

  14. Application limit of Landsat ETM images to detect Saxaul plant community in desert ecosystems

    NASA Astrophysics Data System (ADS)

    Sepehry, Adel; Hassanzadeh, Hassan

    2004-02-01

    Application of satellite remote sensing imageries in studying desert ecosystems is crucial normally due to desert extend, its harsh environment and difficult access which make studying and monitoring of desert ecosystems a cumbersome task. Black Saxaul (Haloxylon Aphyllum), as a resistant plant, is widely planted in Iran"s central deserts to prevent sand dune movement and protect arable lands, roads and buildings from sand debris. An attempt was made to study the effect of Saxaul plantation in Kavir-e-Omrani, in reducing wind erosion and stabilizing sand dunes after 30 years of its plantation in an area of 31627 hectares. Landsat 7 ETM+ imagery acquired on March, 2002 was used to study Saxaul community extent and its canopy cover percentage classes to be related to the field measurements of soil sedimentation depth along prevailing wind direction and through canopy cover percentage gradient of Saxaul community. It was therefore necessary to have canopy cover percentage classes of the community obtained via classification of the ETM images, and their derivative bands. All ETM bands were registered to 1:50000 topographic maps of the area and 10 GCPs obtained by filed measurements using GPS. Correction was made on digitized maps using linear transformation and nearest neighbor method for resampling with RMS error of less than 8 meters. 53 sampling units of 90m by 90m were field checked and canopy cover percentage, density (number of Saxaul per unit area) and ground canopy cover of accompanying plants were measured. Soil samples of ground surface were obtained within each sampling units for lab analysis of soil texture, EC (electric conductivity) and ESP (exchangeable sodium percentage). Coordinates of the corners of sample units were recorded using GPS so that positional discrepancies of sample units were minimized. 16 different vegetation indices, including RVI, NDVI, SAVI, MSAVI and other indices were created. Mean DN values of all ETM bands (except panchromatic

  15. Diffraction-limited soft-x-ray projection imaging using a laser plasma source

    SciTech Connect

    Tichenor, D.A.; Kubiak, G.D.; Malinowski, M.E.; Stulen, R.H.; Haney, S.J.; Berger, K.W.; Brown, L.A. ); Freeman, R.R.; Mansfield, W.M.; Wood, O.R. II; Tennant, D.M.; Bjorkholm, J.E.; MacDowell, A.A. ); Bokor, J.; Jewell, T.E.; White, D.L.; Windt, D.L.; Waskiewicz, W.K. )

    1991-10-15

    Projection imaging of 0.1-{mu}m lines and spaces is demonstrated with a Mo/Si multilayer coated Schwarzschild objective and 14-nm illumination from a laser plasma source. This structure has been etched into a silicon wafer by using a trilevel resist and reactive ion etching. Low-contrast modulation at 0.05-{mu}m lines and spaces is observed in polymethylmethacrylate.

  16. Molecular breast imaging: advantages and limitations of a scintimammographic technique in patients with small breast tumors.

    PubMed

    O'Connor, Michael K; Phillips, Stephen W; Hruska, Carrie B; Rhodes, Deborah J; Collins, Douglas A

    2007-01-01

    Preliminary studies from our laboratory showed that molecular breast imaging (MBI) can reliably detect tumors <2 cm in diameter. This study extends our work to a larger patient population and examines the technical factors that influence the ability of MBI to detect small breast tumors. Following injection of 740 MBq Tc-99m sestamibi, MBI was performed on 100 patients scheduled for biopsy of a lesion suspicious for malignancy that measured <2 cm on mammography or sonography. Using a small field of view gamma camera, patients were imaged in the standard mammographic views using light pain-free compression. Subjective discomfort, breast thickness, the amount of breast tissue in the detector field of view, and breast counts per unit area were measured and recorded. Follow-up was obtained in 99 patients; 53 patients had 67 malignant tumors confirmed at surgery. Of these, 57 of 67 were detected by MBI (sensitivity 85%). Sensitivity was 29%, 86%, and 97% for tumors <5, 6-10, and > or =11 mm in diameter, respectively. In seven patients, MBI identified eight additional mammographically occult tumors. Of 47 patients with no evidence of cancer at biopsy or surgery, there were 36 true negative and 11 false positive scans on MBI. MBI has potential for the regular detection of malignant breast tumors less than 2 cm in diameter. Work in progress to optimize the imaging parameters and technique may further improve sensitivity and specificity. PMID:17214787

  17. Geometrical configurations of unphased diffraction-limited antennas in passive millimetre-wave imaging systems for concealed weapon detection

    NASA Astrophysics Data System (ADS)

    Serenelli, Roberto

    2004-12-01

    This paper analyzes simple imaging configurations to scan a human body, suitable as passive or active millimetre-wave imaging systems for concealed weapon detection (CWD). The first cylindrical configuration allows a 360 degrees scan: N unphased diffraction-limited antennas each of size L are placed on a circular support surrounding the subject (allowing scanning in the horizontal plane with N non-overlapping independent beams), and this circle is mechanically displaced over the whole body height. An analytical formula gives the maximum obtainable spatial resolution for different dimensions of the circular scanning device and operating frequencies, and the number of receivers achieving this optimal resolution. Constraints to be taken into account are diffraction, the usable total length of the circle, and the full coverage by the N beams over the subject, which is modelled as a cylinder with variable radius, coaxial with the scanning circle. Numerical calculations of system resolution are shown for different operating microwave (MW) and millimetre-wave (MMW) frequencies; in order to study off-axis performances, situations where the subject is not coaxial with the scanning device are also considered. For the case of a parallelepiped to be imaged instead of a cylinder, a linear array configuration is analyzed similarly to the circular one. A theoretical study is carried out to design other curved arrays, filled with unphased diffraction-limited antennas, for the imaging of linear subjects with finer resolution. Finally, the application of such configurations is considered for the design of active imaging systems, and different system architectures are discussed.

  18. First-principles theory of Si(110)-(16 × 2) surface reconstruction for unveiling origin of pentagonal scanning tunneling microscopy images

    NASA Astrophysics Data System (ADS)

    Yamasaki, Takahiro; Kato, Koichi; Uda, Tsuyoshi; Yamamoto, Takenori; Ohno, Takahisa

    2016-03-01

    The origin of the scanning tunneling microscopy (STM) zigzag chain structures composed of pairs of pentagons on the Si(110)-(16 × 2) surface is unveiled through the first-principles calculation method. Stable Si(110) surface structures, on both flat and stepped surfaces, have been discovered. The energy gain of the stable step structure is larger than those of previously proposed models by 5.0 eV/(16 × 2) cell or more. The structure consists of buckled tetramers, heptagonal rings, tetragonal rings, and threefold-coordinated Si atoms, but no pentagonal rings. It reproduces the experimental STM images only when frequent flip-floppings of the buckled tetramers at room temperature are considered.

  19. College Students' Concept Images of Asymptotes, Limits, and Continuity of Rational Functions

    ERIC Educational Resources Information Center

    Nair, Girija Sarada

    2010-01-01

    The purpose of this research was to investigate student conceptions of the topic of asymptotes of rational functions and to understand the connections that students developed between the closely related notions of asymptotes, continuity, and limits. The participants of the study were university students taking Calculus 2 and were mostly freshmen. …

  20. A comparison of spatial sampling techniques enabling first principles modeling of a synthetic aperture RADAR imaging platform

    NASA Astrophysics Data System (ADS)

    Gartley, Michael; Goodenough, Adam; Brown, Scott; Kauffman, Russel P.

    2010-04-01

    Simulation of synthetic aperture radar (SAR) imagery may be approached in many different ways. One method treats a scene as a radar cross section (RCS) map and simply evaluates the radar equation, convolved with a system impulse response to generate simulated SAR imagery. Another approach treats a scene as a series of primitive geometric shapes, for which a closed form solution for the RCS exists (such as boxes, spheres and cylinders), and sums their contribution at the antenna level by again solving the radar equation. We present a ray-tracing approach to SAR image simulation that treats a scene as a series of arbitrarily shaped facetized objects, each facet potentially having a unique radio frequency optical property and time-varying location and orientation. A particle based approach, as compared to a wave based approach, presents a challenge for maintaining coherency of sampled scene points between pulses that allows the reconstruction of an exploitable image from the modeled complex phase history. We present a series of spatial sampling techniques and their relative success at producing accurate phase history data for simulations of spotlight, stripmap and SAR-GMTI collection scenarios.

  1. Limitations of anti-scatter grids when used with high resolution image detectors

    NASA Astrophysics Data System (ADS)

    Singh, V.; Jain, A.; Bednarek, D. R.; Rudin, S.

    2014-03-01

    Anti-scatter grids are used in fluoroscopic systems to improve image quality by absorbing scattered radiation. A stationary Smit Rontgen X-ray grid (line density: 70 lines/cm, grid ratio: 13:1) was used with a flat panel detector (FPD) of pixel size 194 micron and a high-resolution CMOS detector, the Dexela 1207 with pixel size of 75 microns. To investigate the effectiveness of the grid, a simulated artery block was placed in a modified uniform frontal head phantom and imaged with both the FPD and the Dexela for an approximately 15 x 15 cm field of view (FOV). The contrast improved for both detectors with the grid. The contrast-to-noise ratio (CNR) does not increase as much in the case of the Dexela as it improves in the case of the FPD. Since the total noise in a single frame increases substantially for the Dexela compared to the FPD when the grid is used, the CNR is degraded. The increase in the quantum noise per frame would be similar for both detectors when the grid is used due to the attenuation of radiation, but the fixed pattern noise caused by the grid was substantially higher for the Dexela compared to the FPD and hence caused a severe reduction of CNR. Without further corrective methods this grid should not be used with high-resolution fluoroscopic detectors because the CNR does not improve significantly and the visibility of low contrast details may be reduced. Either an anti-scatter grid of different design or an additional image processing step when using a similar grid would be required to deal with the problem of scatter for high resolution detectors and the structured noise of the grid pattern.

  2. Limitations of anti-scatter grids when used with high resolution image detectors.

    PubMed

    Singh, V; Jain, A; Bednarek, D R; Rudin, S

    2014-03-19

    Anti-scatter grids are used in fluoroscopic systems to improve image quality by absorbing scattered radiation. A stationary Smit Rontgen X-ray grid (line density: 70 lines/cm, grid ratio: 13:1) was used with a flat panel detector (FPD) of pixel size 194 micron and a high-resolution CMOS detector, the Dexela 1207 with pixel size of 75 microns. To investigate the effectiveness of the grid, a simulated artery block was placed in a modified uniform frontal head phantom and imaged with both the FPD and the Dexela for an approximately 15 × 15 cm field of view (FOV). The contrast improved for both detectors with the grid. The contrast-to-noise ratio (CNR) does not increase as much in the case of the Dexela as it improves in the case of the FPD. Since the total noise in a single frame increases substantially for the Dexela compared to the FPD when the grid is used, the CNR is degraded. The increase in the quantum noise per frame would be similar for both detectors when the grid is used due to the attenuation of radiation, but the fixed pattern noise caused by the grid was substantially higher for the Dexela compared to the FPD and hence caused a severe reduction of CNR. Without further corrective methods this grid should not be used with high-resolution fluoroscopic detectors because the CNR does not improve significantly and the visibility of low contrast details may be reduced. Either an anti-scatter grid of different design or an additional image processing step when using a similar grid would be required to deal with the problem of scatter for high resolution detectors and the structured noise of the grid pattern. PMID:25309101

  3. Analysis of the Advantages and Limitations of Stationary Imaging Fourier Transform Spectrometer. Revised

    NASA Technical Reports Server (NTRS)

    Beecken, Brian P.; Kleinman, Randall R.

    2004-01-01

    New developments in infrared sensor technology have potentially made possible a new space-based system which can measure far-infrared radiation at lower costs (mass, power and expense). The Stationary Imaging Fourier Transform Spectrometer (SIFTS) proposed by NASA Langley Research Center, makes use of new detector array technology. A mathematical model which simulates resolution and spectral range relationships has been developed for analyzing the utility of such a radically new approach to spectroscopy. Calculations with this forward model emulate the effects of a detector array on the ability to retrieve accurate spectral features. Initial computations indicate significant attenuation at high wavenumbers.

  4. Type-Ia SN 2016coj - limits on progenitors from pre-explosion HST images

    NASA Astrophysics Data System (ADS)

    Friedmann, Matan; Maoz, Dan

    2016-07-01

    We have analyzed archival Hubble Space Telescope WFPC2 images of the site of the Type-Ia SN2016coj (ATEL#9095, #9193) in NGC 4125 in five filters taken on several pre-explosion epochs: F336W from 2009 (~U band, 6600 s total), F439W from 2009 (~B band, 2100 s total), F555W from 1999 (~V band, 1400 s total), F702W from 1997 (~R band, 1000 s total) and F814W (~I band, 2000 s total).

  5. Sub-diffraction Limit Localization of Proteins in Volumetric Space Using Bayesian Restoration of Fluorescence Images from Ultrathin Specimens

    PubMed Central

    Wang, Gordon; Smith, Stephen J.

    2012-01-01

    Photon diffraction limits the resolution of conventional light microscopy at the lateral focal plane to 0.61λ/NA (λ = wavelength of light, NA = numerical aperture of the objective) and at the axial plane to 1.4nλ/NA2 (n = refractive index of the imaging medium, 1.51 for oil immersion), which with visible wavelengths and a 1.4NA oil immersion objective is ∼220 nm and ∼600 nm in the lateral plane and axial plane respectively. This volumetric resolution is too large for the proper localization of protein clustering in subcellular structures. Here we combine the newly developed proteomic imaging technique, Array Tomography (AT), with its native 50–100 nm axial resolution achieved by physical sectioning of resin embedded tissue, and a 2D maximum likelihood deconvolution method, based on Bayes' rule, which significantly improves the resolution of protein puncta in the lateral plane to allow accurate and fast computational segmentation and analysis of labeled proteins. The physical sectioning of AT allows tissue specimens to be imaged at the physical optimum of modern high NA plan-apochormatic objectives. This translates to images that have little out of focus light, minimal aberrations and wave-front distortions. Thus, AT is able to provide images with truly invariant point spread functions (PSF), a property critical for accurate deconvolution. We show that AT with deconvolution increases the volumetric analytical fidelity of protein localization by significantly improving the modulation of high spatial frequencies up to and potentially beyond the spatial frequency cut-off of the objective. Moreover, we are able to achieve this improvement with no noticeable introduction of noise or artifacts and arrive at object segmentation and localization accuracies on par with image volumes captured using commercial implementations of super-resolution microscopes. PMID:22956902

  6. Management of occult adrenocorticotropin-secreting bronchial carcinoids: limits of endocrine testing and imaging techniques.

    PubMed

    Loli, P; Vignati, F; Grossrubatscher, E; Dalino, P; Possa, M; Zurleni, F; Lomuscio, G; Rossetti, O; Ravini, M; Vanzulli, A; Bacchetta, C; Galli, C; Valente, D

    2003-03-01

    The differential diagnosis and the identification of the source of ACTH in occult ectopic Cushing's syndrome due to a bronchial carcinoid still represents a challenge for the endocrinologist. We report our experience in six patients with occult bronchial carcinoid in whom extensive hormonal, imaging, and scintigraphic evaluation was performed. All patients presented with hypercortisolism associated with high plasma ACTH values. The CRH test and high dose dexamethasone suppression test suggested an ectopic source of ACTH in three of six patients. During bilateral inferior petrosal sinus sampling, none of the patients showed a central to peripheral ACTH gradient. At the time of diagnosis, none of the patients had radiological evidence of the ectopic source of ACTH, whereas pentetreotide scintigraphy identified the lesion in two of four patients. Finally, a chest computed tomography scan revealed the presence of a bronchial lesion in all patients, and pentetreotide scintigraphy identified four of six lesions. In all patients a bronchial carcinoid was found and removed. In one patient with scintigraphic evidence of residual disease after two operations, radioguided surgery, using a hand-held gamma probe after iv administration of radiolabeled pentetreotide, was performed; this allowed detection and removal of residual multiple mediastinal lymph node metastases. In conclusion, our data show that there is not a single endocrine test or imaging procedure accurate enough to diagnose and localize occult ectopic ACTH-secreting bronchial carcinoids. Radioguided surgery appears to be promising in the presence of multiple tumor foci and previous incomplete removal of the tumor. PMID:12629081

  7. Nonparametric feature extraction for classification of hyperspectral images with limited training samples

    NASA Astrophysics Data System (ADS)

    Kianisarkaleh, Azadeh; Ghassemian, Hassan

    2016-09-01

    Feature extraction plays a crucial role in improvement of hyperspectral images classification. Nonparametric feature extraction methods show better performance compared to parametric ones when distribution of classes is non normal-like. Moreover, they can extract more features than parametric methods do. In this paper, a new nonparametric linear feature extraction method is introduced for classification of hyperspectral images. The proposed method has no free parameter and its novelty can be discussed in two parts. First, neighbor samples are specified by using Parzen window idea for determining local mean. Second, two new weighting functions are used. Samples close to class boundaries will have more weight in the between-class scatter matrix formation and samples close to class mean will have more weight in the within-class scatter matrix formation. The experimental results on three real hyperspectral data sets, Indian Pines, Salinas and Pavia University, demonstrate that the proposed method has better performance in comparison with some other nonparametric and parametric feature extraction methods.

  8. Binary Image Classification: A Genetic Programming Approach to the Problem of Limited Training Instances.

    PubMed

    Al-Sahaf, Harith; Zhang, Mengjie; Johnston, Mark

    2016-01-01

    In the computer vision and pattern recognition fields, image classification represents an important yet difficult task. It is a challenge to build effective computer models to replicate the remarkable ability of the human visual system, which relies on only one or a few instances to learn a completely new class or an object of a class. Recently we proposed two genetic programming (GP) methods, one-shot GP and compound-GP, that aim to evolve a program for the task of binary classification in images. The two methods are designed to use only one or a few instances per class to evolve the model. In this study, we investigate these two methods in terms of performance, robustness, and complexity of the evolved programs. We use ten data sets that vary in difficulty to evaluate these two methods. We also compare them with two other GP and six non-GP methods. The results show that one-shot GP and compound-GP outperform or achieve results comparable to competitor methods. Moreover, the features extracted by these two methods improve the performance of other classifiers with handcrafted features and those extracted by a recently developed GP-based method in most cases. PMID:25700148

  9. Line imaging ladar using a laser-diode transmitter and FM/cw radar principles for submunition applications

    NASA Astrophysics Data System (ADS)

    Stann, Barry L.; Abou-Auf, Ahmed; Ruff, William C.; Robinson, Dale; Liss, Brian; Potter, William; Sarama, Scott D.; Giza, Mark M.; Simon, Deborah R.; Frankel, Scott; Sztankay, Zoltan G.

    2000-09-01

    We describe the technical approach, component development, and test results of a line imager laser radar (ladar) being developed at the Army Research Laboratory (ARL) for smart munition applications. We obtain range information using a frequency modulation/continuous wave (FM/cw) technique implemented by directly amplitude modulating a near-IR diode laser transmitter with a radio frequency (rf) subcarrier that is linearly frequency modulated. The diode's output is collimated and projected to form a line illumination in the downrange image area. The returned signal is focused onto a line array of metal-semiconductor-metal (MSM) detectors where it is detected and mixed with a delayed replica of the laser modulation signal that modulates the responsivity of each detector. The output of each detector is an intermediate frequency (IF) signal (a product of the mixing process) whose frequency is proportional to the target range. This IF signal is continuously sampled over each period of the rf modulation. Following this, a N-channel signal processor based on field- programmable gate arrays (FPGA) calculates the discrete Fourier transform over the IF waveform in each pixel to establish the ranges to all the scatterers and their respective amplitudes. Over the past year, we constructed the fundamental building blocks of this ladar, which include a 3.5-W line illuminator, a wideband linear FM chirp modulator, a N-pixel MSM detector line array, and a N-channel FPGA signal processor. In this paper we report on the development and performance of each building block and the results of system tests conducted in the laboratory.

  10. Determination of optimal imaging parameters for the reconstruction of a nuclear fuel assembly using limited angle neutron tomography

    NASA Astrophysics Data System (ADS)

    Abir, M. I.; Islam, F. F.; Craft, A.; Williams, W. J.; Wachs, D. M.; Chichester, D. L.; Meyer, M. K.; Lee, H. K.

    2016-01-01

    The core components of nuclear reactors (e.g., fuel assemblies, spacer grids, control rods) encounter harsh environments due to high temperature, physical stress, and a tremendous level of radiation. The integrity of these elements is crucial for safe operation of nuclear power plants; post-irradiation examination (PIE) can reveal information about the integrity of these components. Neutron computed tomography (CT) is one important PIE measurement tool for nondestructively evaluating the structural integrity of these items. CT typically requires many projections to be acquired from different view angles, after which a mathematical algorithm is used for image reconstruction. However, when working with heavily irradiated materials and irradiated nuclear fuel, obtaining many projections is laborious and expensive. Image reconstruction from a smaller number of projections has been explored to achieve faster and more cost-efficient PIE. Classical reconstruction methods (e.g., filtered backprojection), unfortunately, do not typically offer stable reconstructions from a highly asymmetric, few-projection data set and often create severe streaking artifacts. We propose an iterative reconstruction technique to reconstruct curved, plate-type nuclear fuel assemblies using limited-angle CT. The performance of the proposed method is assessed using simulated data and validated through real projections. We also discuss the systematic strategy for establishing the conditions of reconstructions and finding the optimal imaging parameters for reconstructions of the fuel assemblies from few projections using limited-angle CT. Results show that a fuel assembly can be reconstructed using limited-angle CT if 36 or more projections are taken from a particular direction with 1° angular increment.

  11. Maximum precision closed-form solution for localizing diffraction-limited spots in noisy images

    PubMed Central

    Larkin, Joshua D.; Cook, Peter R.

    2012-01-01

    Super-resolution techniques like PALM and STORM require accurate localization of single fluorophores detected using a CCD. Popular localization algorithms inefficiently assume each photon registered by a pixel can only come from an area in the specimen corresponding to that pixel (not from neighboring areas), before iteratively (slowly) fitting a Gaussian to pixel intensity; they fail with noisy images. We present an alternative; a probability distribution extending over many pixels is assigned to each photon, and independent distributions are joined to describe emitter location. We compare algorithms, and recommend which serves best under different conditions. At low signal-to-noise ratios, ours is 2-fold more precise than others, and 2 orders of magnitude faster; at high ratios, it closely approximates the maximum likelihood estimate. PMID:23038398

  12. IR Image upconversion using band-limited ASE illumination fiber sources.

    PubMed

    Maestre, H; Torregrosa, A J; Capmany, J

    2016-04-18

    We study the field-of-view (FOV) of an upconversion imaging system that employs an Amplified Spontaneous Emission (ASE) fiber source to illuminate a transmission target. As an intermediate case between narrowband laser and thermal illumination, an ASE fiber source allows for higher spectral intensity than thermal illumination and still keeps a broad wavelength spectrum to take advantage of an increased non-collinear phase-matching angle acceptance that enlarges the FOV of the upconversion system when compared to using narrowband laser illumination. A model is presented to predict the angular acceptance of the upconverter in terms of focusing and ASE spectral width and allocation. The model is experimentally checked in case of 1550-630 nm upconversion. PMID:27137295

  13. Magnetic resonance imaging of the central nervous system

    SciTech Connect

    Brant-Zawadzki, M.; Norman, D.

    1987-01-01

    This book presents the papers on technological advancement and diagnostic uses g magnetic resonance imaging. A comparative evaluation with computerized tomography is presented. Topics covered are imaging principles g magnetic resonance;instrumentation of magnetic resonance (MR);pathophysiology;quality and limitations g images;NMR imaging of brain and spinal cord;MR spectroscopy and its applications;neuroanatomy;Congenital malformations of brain and MR imaging;planning g MR imaging of spine and head and neck imaging.

  14. Limitations of symmetry in FE modeling: A comparison of fem and air-coupled resonance imaging

    NASA Astrophysics Data System (ADS)

    Livings, R. A.; Dayal, V.; Barnard, D. J.; Hsu, D. K.

    2012-05-01

    It has long been an accepted practice to use symmetry in Finite Element Modeling. Whenever modeling a large structure, we turn to symmetry in order to significantly reduce the model size and computation time. But is symmetry always the solution to long computation times, and is it always accurate? This study is aimed at modeling a whole ceramic tile and several possible symmetric models under several different loading cases and comparing them to each other and Air-Coupled Ultrasonic scans to determine if the Finite Element Models can accurately predict the vibrational resonance patterns. The reason for the accuracy or inaccuracy will also be examined. The understanding of the limitations of using symmetry to model large structures will be very useful in all future modeling.

  15. Principles for an interactive multi-scale assessment of sustainable production limits - lessons from the Limpopo river basin case, South Africa

    NASA Astrophysics Data System (ADS)

    Froebrich, Jochen; de Cleccq, Willem; Veraart, Jeroen; Vullings, Wies

    2015-04-01

    About 7.2 billion people currently live on the Earth and the population is projected to reach 9.6 billion by 2050, that growth will be mainly in developing countries, with more than half in Africa (United Nations 2013). Any local extension of irrigated agriculture in a region of scarce natural resources may potentially restrict the possibility to extend land and water use at another location of the same river basin. In order to support, develop and to assess such future interventions, it is important to define limits until which a sustainable production can take place at a given location, taking into account competing claims on natural resources, human welfare and impacts on environmental quality. We define Sustainable production limits as limits for the possible resource use, within which a production can be extended without restricting the growth opportunities at a neighboured location. The more threatened the natural resources become, the more important it is to consider the effect of other upcoming interventions within the same region. As a consequence, interventions for future resource use have to be assessed against the future available natural resources. This is of particular relevance for evaluating possible extensions of irrigation areas within a river basin. Investigating possible limits for extending irrigated agriculture at local scale requires an understanding of the complexity, including boundaries, activities, stakeholders, and opportunities at river basin scale, and more. Switching between the scales in this information, in a participatory process, appears to be a challenge in its own. Within the Limpopo River basin (South Africa), we analysed (i) possible interventions at local scale (transdisciplinary innovation of irrigation by smallholders, launching of PPPs), (ii) restrictions for developing irrigation at the Letaba sub basin scale, and (iii) water balance at the scale of the Limpopo basin. Experiences from the Limpopo case revealed, that

  16. Limitation of imaging in identifying iatrogenic aortic coarctation following thoracic endovascular aortic repair.

    PubMed

    Thakkar, Rajiv N; Thomaier, Lauren; Qazi, Umair; Verde, Franco; Malas, Mahmoud B

    2015-04-01

    A 21-year-old male suffered blunt trauma from a motor vehicle accident causing thoracic aorta tear. The smallest available stent graft was deployed. Definitive repair was later performed using a 22 × 22 × 116 mm Talent Thoracic Stent Graft. The postoperative course was uneventful. Seventeen months later, he presented with dizziness, chest pain, acute renal failure, malignant hypertension, and troponin elevation. Computed tomography (CT) angiogram and transesophageal echocardiogram did not reveal any dissection, stent stenosis or collapse. Cardiac catheterization showed normal coronary arteries but a 117 mm Hg gradient across the stent graft. Iatrogenic coarctation of the aorta was confirmed with a second measurement during arch angiogram. A Palmaz stent was deployed over the distal end of the previous stent graft with complete resolution of symptoms and gradual normalization of kidney function. This case report demonstrates a need for wider availability and selecting appropriate stent graft in treating traumatic aortic injuries in young patients. It is the first case report of the inability of current imaging modalities in confirming stent collapse. Pressure gradient is a useful tool in confirming stent collapse when clinical scenario does not match CT findings. PMID:25637574

  17. Fundamental Limits on the Imaging and Polarisation Properties of Far-Infrared Detectors

    NASA Technical Reports Server (NTRS)

    Thomas, Christopher N.; Withington, Stafford; Chuss, David T.; Wollack, Edward J.; Moseley, S. Harvey

    2009-01-01

    Far-infrared bolometric detectors are used extensively in ground-based and space-borne astronomy, and thus it is important to understand their optical behaviour precisely. We have studied the intensity and polarisation response of free-space bolometers, and shown that when the size of the absorber is reduced below a wavelength, the response changes from being that of a classical optical detector to that of a few-mode antenna. We have calculated the modal content of the reception patterns, and found that for any volumetric detector having a side length of less than a wavelength, three magnetic and three electric dipoles characterize the behaviour. The size of the absorber merely determines the relative strengths of the contributions. The same formalism can be applied to thin-film absorbers, where the induced current is forced to flow in a plane. In this case, one magnetic and two electric dipoles characterize the behaviour. The ability to model easily the intensity, polarisation, and straylight characteristics of electrically-small detectors will be of great value when designing high-performance polarimetric imaging arrays.

  18. Data Reduction Pipeline for OSIRIS, the new NIR Diffraction Limited Imaging Field Spectrometer for the Keck Adaptive Optics System

    NASA Astrophysics Data System (ADS)

    Krabbe, Alfred; Gasaway, Thomas M.; Weiss, Jason; Larkin, James E.; Barczys, Matthew; Quirrenbach, Andreas; LaFreniere, David

    2002-12-01

    OSIRIS is a near infrared diffraction limited imaging field spectrometer under development for the Keck observatory adaptive optics system. Based upon lenslet pupil imaging, diffraction grating, and a 2K×2K Hawaii2 HgCdTe array, OSIRIS is a highly efficient instrument at the forefront of today"s technology. OSIRIS will deliver per readout up to 4096 diffraction limited spectra in a complex interleaved format, requiring new challenges to be met regarding user interaction and data reduction. A data reduction software package is under development, aiming to provide the observer with a facility instrument allowing him to concentrate on science rather than dealing with instrumental as well as telescope and atmosphere related effects. Together with OSIRIS, a pipeline for basic data reduction will be provided for a new Keck instrument for the first time. Some aspects of the data reduction pipeline will be presented here. The OSIRIS instrument as such, the astronomical background as well as other software tools were presented elsewhere on this conference.

  19. Pushing back the limits of Raman imaging by coupling super-resolution and chemometrics for aerosols characterization

    PubMed Central

    Offroy, Marc; Moreau, Myriam; Sobanska, Sophie; Milanfar, Peyman; Duponchel, Ludovic

    2015-01-01

    The increasing interest in nanoscience in many research fields like physics, chemistry, and biology, including the environmental fate of the produced nano-objects, requires instrumental improvements to address the sub-micrometric analysis challenges. The originality of our approach is to use both the super-resolution concept and multivariate curve resolution (MCR-ALS) algorithm in confocal Raman imaging to surmount its instrumental limits and to characterize chemical components of atmospheric aerosols at the level of the individual particles. We demonstrate the possibility to go beyond the diffraction limit with this algorithmic approach. Indeed, the spatial resolution is improved by 65% to achieve 200 nm for the considered far-field spectrophotometer. A multivariate curve resolution method is then coupled with super-resolution in order to explore the heterogeneous structure of submicron particles for describing physical and chemical processes that may occur in the atmosphere. The proposed methodology provides new tools for sub-micron characterization of heterogeneous samples using far-field (i.e. conventional) Raman imaging spectrometer. PMID:26201867

  20. Protein biomarkers on tissue as imaged via MALDI mass spectrometry: A systematic approach to study the limits of detection.

    PubMed

    van de Ven, Stephanie M W Y; Bemis, Kyle D; Lau, Kenneth; Adusumilli, Ravali; Kota, Uma; Stolowitz, Mark; Vitek, Olga; Mallick, Parag; Gambhir, Sanjiv S

    2016-06-01

    MALDI mass spectrometry imaging (MSI) is emerging as a tool for protein and peptide imaging across tissue sections. Despite extensive study, there does not yet exist a baseline study evaluating the potential capabilities for this technique to detect diverse proteins in tissue sections. In this study, we developed a systematic approach for characterizing MALDI-MSI workflows in terms of limits of detection, coefficients of variation, spatial resolution, and the identification of endogenous tissue proteins. Our goal was to quantify these figures of merit for a number of different proteins and peptides, in order to gain more insight in the feasibility of protein biomarker discovery efforts using this technique. Control proteins and peptides were deposited in serial dilutions on thinly sectioned mouse xenograft tissue. Using our experimental setup, coefficients of variation were <30% on tissue sections and spatial resolution was 200 μm (or greater). Limits of detection for proteins and peptides on tissue were in the micromolar to millimolar range. Protein identification was only possible for proteins present in high abundance in the tissue. These results provide a baseline for the application of MALDI-MSI towards the discovery of new candidate biomarkers and a new benchmarking strategy that can be used for comparing diverse MALDI-MSI workflows. PMID:26970438

  1. Pushing back the limits of Raman imaging by coupling super-resolution and chemometrics for aerosols characterization

    NASA Astrophysics Data System (ADS)

    Offroy, Marc; Moreau, Myriam; Sobanska, Sophie; Milanfar, Peyman; Duponchel, Ludovic

    2015-07-01

    The increasing interest in nanoscience in many research fields like physics, chemistry, and biology, including the environmental fate of the produced nano-objects, requires instrumental improvements to address the sub-micrometric analysis challenges. The originality of our approach is to use both the super-resolution concept and multivariate curve resolution (MCR-ALS) algorithm in confocal Raman imaging to surmount its instrumental limits and to characterize chemical components of atmospheric aerosols at the level of the individual particles. We demonstrate the possibility to go beyond the diffraction limit with this algorithmic approach. Indeed, the spatial resolution is improved by 65% to achieve 200 nm for the considered far-field spectrophotometer. A multivariate curve resolution method is then coupled with super-resolution in order to explore the heterogeneous structure of submicron particles for describing physical and chemical processes that may occur in the atmosphere. The proposed methodology provides new tools for sub-micron characterization of heterogeneous samples using far-field (i.e. conventional) Raman imaging spectrometer.

  2. Analysis of MUSIC-type imaging functional for single, thin electromagnetic inhomogeneity in limited-view inverse scattering problem

    NASA Astrophysics Data System (ADS)

    Ahn, Chi Young; Jeon, Kiwan; Park, Won-Kwang

    2015-06-01

    This study analyzes the well-known MUltiple SIgnal Classification (MUSIC) algorithm to identify unknown support of thin penetrable electromagnetic inhomogeneity from scattered field data collected within the so-called multi-static response matrix in limited-view inverse scattering problems. The mathematical theories of MUSIC are partially discovered, e.g., in the full-view problem, for an unknown target of dielectric contrast or a perfectly conducting crack with the Dirichlet boundary condition (Transverse Magnetic-TM polarization) and so on. Hence, we perform further research to analyze the MUSIC-type imaging functional and to certify some well-known but theoretically unexplained phenomena. For this purpose, we establish a relationship between the MUSIC imaging functional and an infinite series of Bessel functions of integer order of the first kind. This relationship is based on the rigorous asymptotic expansion formula in the existence of a thin inhomogeneity with a smooth supporting curve. Various results of numerical simulation are presented in order to support the identified structure of MUSIC. Although a priori information of the target is needed, we suggest a least condition of range of incident and observation directions to apply MUSIC in the limited-view problem.

  3. Design, simulation, and fabrication of a 90° SOI optical hybrid based on the self-imaging principle

    NASA Astrophysics Data System (ADS)

    Abdul-Majid, Sawsan; Hasan, Imad I.; Bock, Przemek J.; Hall, Trevor J.

    2010-05-01

    This paper introduces a compact 90º optical hybrid, built on small size SOI waveguide technology .This optical hybrid is a critical component of a potentially low-cost coherent optical receiver design developed within the frame of our Optical Coherent Transmission for Access Network Extensions (OCTANE) project. In previous recent work, 90º optical hybrids were realized in SOI rib waveguide technology with 4 μm top silicon and a rib height of approximately 2 μm. In this paper, we introduce a compact 90º optical hybrid, built on small size SOI waveguide technology (1.5 μm SOI -based rib waveguide, with 0.8μm rib height). The proposed device consists of multimode interferometers (MMIs) connected in such a way that four different vector additions of a reference signal (local oscillator) and the signal to be detected are obtained. At the outputs, the hybrid provides four linear combination of the signal with the reference which differs by a relative phase shift of the reference of 90º. The four output signals are detected by a pair of balanced receivers to provide in-phase and quadrature (I&Q) channels. The phase differences arise naturally from the self imaging property of a MMI. The key elements of the 90º optical hybrid, including a 2×2 MMI, a 4×4 MMI, and polarization diversity configuration have been designed and simulated, using the numerical mode solving tool FIMMPROB. The 2×2 and 4×4 MMI had overall lengths of 701μm and 3712.5μm lengths respectively. Tapers are used to couple adiabatically single mode waveguides to the entrance and exit ports of the MMI to assure correct operation by avoiding coupling to the higher order transverse modes allowed at the entrance and exit ports of the MMI. The simulation results at 1550nm show polarization independence and phase errors between the ports of less than 0.03 degrees. Currently the design is in fabrication at the Canadian Photonics Fabrication Center with the support of CMC Microsystems and experimental

  4. Crossing the Resolution Limit in Near-Infrared Imaging of Silicon Chips: Targeting 10-nm Node Technology

    NASA Astrophysics Data System (ADS)

    Agarwal, Krishna; Chen, Rui; Koh, Lian Ser; Sheppard, Colin J. R.; Chen, Xudong

    2015-04-01

    The best reported resolution in optical failure analysis of silicon chips is 120-nm half pitch demonstrated by Semicaps Private Limited, whereas the current and future industry requirement for 10-nm node technology is 100-nm half pitch. We show the first experimental evidence for resolution of features with 100-nm half pitch buried in silicon (λ /10.6 ), thus fulfilling the industry requirement. These results are obtained using near-infrared reflection-mode imaging using a solid immersion lens. The key novel feature of our approach is the choice of an appropriately sized collection pinhole. Although it is usually understood that, in general, resolution is improved by using the smallest pinhole consistent with an adequate signal level, it is found that in practice for silicon chips there is an optimum pinhole size, determined by the generation of induced currents in the sample. In failure analysis of silicon chips, nondestructive imaging is important to avoid disturbing the functionality of integrated circuits. High-resolution imaging techniques like SEM or TEM require the transistors to be exposed destructively. Optical microscopy techniques may be used, but silicon is opaque in the visible spectrum, mandating the use of near-infrared light and thus poor resolution in conventional optical microscopy. We expect our result to change the way semiconductor failure analysis is performed.

  5. Limited Ability of Posaconazole To Cure both Acute and Chronic Trypanosoma cruzi Infections Revealed by Highly Sensitive In Vivo Imaging

    PubMed Central

    Francisco, Amanda Fortes; Lewis, Michael D.; Jayawardhana, Shiromani; Taylor, Martin C.; Chatelain, Eric

    2015-01-01

    The antifungal drug posaconazole has shown significant activity against Trypanosoma cruzi in vitro and in experimental murine models. Despite this, in a recent clinical trial it displayed limited curative potential. Drug testing is problematic in experimental Chagas disease because of difficulties in demonstrating sterile cure, particularly during the chronic stage of infection when parasite burden is extremely low and tissue distribution is ill defined. To better assess posaconazole efficacy against acute and chronic Chagas disease, we have exploited a highly sensitive bioluminescence imaging system which generates data with greater accuracy than other methods, including PCR-based approaches. Mice inoculated with bioluminescent T. cruzi were assessed by in vivo and ex vivo imaging, with cyclophosphamide-induced immunosuppression used to enhance the detection of relapse. Posaconazole was found to be significantly inferior to benznidazole as a treatment for both acute and chronic T. cruzi infections. Whereas 20 days treatment with benznidazole was 100% successful in achieving sterile cure, posaconazole failed in almost all cases. Treatment of chronic infections with posaconazole did however significantly reduce infection-induced splenomegaly, even in the absence of parasitological cure. The imaging-based screening system also revealed that adipose tissue is a major site of recrudescence in mice treated with posaconazole in the acute, but not the chronic stage of infection. This in vivo screening model for Chagas disease is predictive, reproducible and adaptable to diverse treatment schedules. It should provide greater assurance that drugs are not advanced prematurely into clinical trial. PMID:26014936

  6. Performance and Limitations of Positron Emission Tomography (PET) Scanners for Imaging Very Low Activity Sources

    PubMed Central

    Freedenberg, Melissa; Badawi, Ramsey D.; Tarantal, Alice F.; Cherry, Simon R.

    2013-01-01

    Emerging applications for positron emission tomography (PET) may require the ability to image very low activity source distributions in the body. The performance of clinical PET scanners in the regime where activity in the field of view is <1 MBq has not previously been explored. In this study, we compared the counting rate performance of two clinical PET/CT scanners, the Siemens Biograph Reveal 16 scanner which is based on lutetium oxyorthosilicate (LSO) detectors and the GE Discovery-ST scanner which is based on bismuth germanate (BGO) detectors using a modified National Electrical Manufacturers Association (NEMA) NU 2-2007 protocol. Across the activity range studied (2-100 kBq/mL in a 5.5 mL line source in the NEMA scatter phantom), the BGO-based scanner significantly outperformed the LSO-based scanner. This was largely due to the effect of background counts emanating from naturally occurring but radioactive 176Lu within the LSO detector material, which dominates the observed counting rate at the lowest activities. Increasing the lower energy threshold from 350 keV to 425 keV in an attempt to reduce this background did not significantly improve the measured NECR performance. The measured singles rate due to 176Lu emissions within the scanner energy window was also found to be dependent on temperature, and to be affected by the operation of CT component, making approaches to correct or compensate for the background more challenging. We conclude that for PET studies in a very low activity range, BGO-based scanners are likely to have better performance because of the lack of significant background. PMID:23680361

  7. Fundamental limitations to the spatial resolution and flow volume that can be mapped using holographic particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Coupland, Jeremy M.; Lobera Salazar, Julia; Halliwell, Neil A.

    2000-08-01

    We have recently proposed a variant of holographic particle image velocimetry (HPIV) to measure three-component measurements of fluid velocity throughout an extended flow volume. In essence the technique uses double exposure holography to record the positions of seeding particles at two, close spaced constants in time. Analysis of the resulting record is achieved by computing the auto (or cross) correlation of the complex amplitude distributions transmitted by a sampling aperture placed within a real, reconstruction of the holographic image. IN the case of sparsely seeded flows, it is straightforward to show that the field transmitted by the aperture is dominated by the particle images reconstructed close to the aperture itself and the measurement is therefore attributed to the instantaneous flow velocity at the centre of the aperture. As the seeding concentration is increased, however, a significant contribution of the transmitted field is due to light scattered from more distant particles. If significant velocity gradients exist, the contribution due to distant particles is largely un- correlated and the local particle displacement can be extracted even if the field is dominated by this component. If a significant proportion of the scattered light that passes from the aperture is collected from areas in the flow with similar velocity (for example from stagnant regions or light scattered from the flow vessel) then spurious peaks can occur in the correlation signal. This paper examines the limitations on the flow volume that can be mapped at a given seeding concentration and hence the fundamental limits on the number of velocity measurements that can be retrieved from a single recording.

  8. Schlieren imaging of loud sounds and weak shock waves in air near the limit of visibility

    NASA Astrophysics Data System (ADS)

    Hargather, Michael John; Settles, Gary S.; Madalis, Matthew J.

    2010-02-01

    A large schlieren system with exceptional sensitivity and a high-speed digital camera are used to visualize loud sounds and a variety of common phenomena that produce weak shock waves in the atmosphere. Frame rates varied from 10,000 to 30,000 frames/s with microsecond frame exposures. Sound waves become visible to this instrumentation at frequencies above 10 kHz and sound pressure levels in the 110 dB (6.3 Pa) range and above. The density gradient produced by a weak shock wave is examined and found to depend upon the profile and thickness of the shock as well as the density difference across it. Schlieren visualizations of weak shock waves from common phenomena include loud trumpet notes, various impact phenomena that compress a bubble of air, bursting a toy balloon, popping a champagne cork, snapping a wooden stick, and snapping a wet towel. The balloon burst, snapping a ruler on a table, and snapping the towel and a leather belt all produced readily visible shock-wave phenomena. In contrast, clapping the hands, snapping the stick, and the champagne cork all produced wave trains that were near the weak limit of visibility. Overall, with sensitive optics and a modern high-speed camera, many nonlinear acoustic phenomena in the air can be observed and studied.

  9. High-resolution imaging and spectroscopy of interfacial water at single bond limit

    NASA Astrophysics Data System (ADS)

    Jiang, Ying

    Hydrogen bond is one of the most important weak interactions in nature and plays an essential role in a broad spectrum of physics, chemistry, biology, energy and material sciences. The conventional methods for studying hydrogen-bonding interaction are all based on spectroscopic or diffraction techniques. However, those techniques have poor spatial resolution and only measure the average properties of many hydrogen bonds, which are susceptible to the structural inhomogeneity and local environments, especially when interfacial systems are concerned. The spatial variation and inter-bond coupling of the hydrogen bonds leads to significant spectral broadening, which prohibits the accurate understanding of the experimental data. In this talk, I will present our recent progress on the development of new-generation scanning probe microscopy/spectroscopy (SPM/S) with unprecedentedly high sensitivity and resolution, for addressing weak inter- and intra-molecular interactions, such as hydrogen bonds and van der Waals force. Based on a qPlus sensor, we have succeeded to push the real-space study of a prototypical hydrogen-bonded system, i.e. water, down to single bond limit. Combined with state-of-the-arts quantum simulations, we have discovered exotic nuclear quantum effects (NQEs) in interfacial water and revealed the quantum nature of the hydrogen bond from a completely new perspective

  10. Printable Nanoscopic Metamaterial Absorbers and Images with Diffraction-Limited Resolution.

    PubMed

    Richner, Patrizia; Eghlidi, Hadi; Kress, Stephan J P; Schmid, Martin; Norris, David J; Poulikakos, Dimos

    2016-05-11

    The fabrication of functional metamaterials with extreme feature resolution finds a host of applications such as the broad area of surface/light interaction. Nonplanar features of such structures can significantly enhance their performance and tunability, but their facile generation remains a challenge. Here, we show that carefully designed out-of-plane nanopillars made of metal-dielectric composites integrated in a metal-dielectric-nanocomposite configuration can absorb broadband light very effectively. We further demonstrate that electrohydrodynamic printing in a rapid nanodripping mode is able to generate precise out-of-plane forests of such composite nanopillars with deposition resolutions at the diffraction limit on flat and nonflat substrates. The nanocomposite nature of the printed material allows the fine-tuning of the overall visible light absorption from complete absorption to complete reflection by simply tuning the pillar height. Almost perfect absorption (∼95%) over the entire visible spectrum is achieved by a nanopillar forest covering only 6% of the printed area. Adjusting the height of individual pillar groups by design, we demonstrate on-demand control of the gray scale of a micrograph with a spatial resolution of 400 nm. These results constitute a significant step forward in ultrahigh resolution facile fabrication of out-of-plane nanostructures, important to a broad palette of light design applications. PMID:27100105

  11. Medical Imaging Physics, 4th Edition

    NASA Astrophysics Data System (ADS)

    Hendee, William R.; Ritenour, E. Russell

    2002-05-01

    This comprehensive publication covers all aspects of image formation in modern medical imaging modalities, from radiography, fluoroscopy, and computed tomography, to magnetic resonance imaging and ultrasound. It addresses the techniques and instrumentation used in the rapidly changing field of medical imaging. Now in its fourth edition, this text provides the reader with the tools necessary to be comfortable with the physical principles, equipment, and procedures used in diagnostic imaging, as well as appreciate the capabilities and limitations of the technologies.

  12. Fundamental x-ray interaction limits in diagnostic imaging detectors: frequency-dependent Swank noise.

    PubMed

    Hajdok, G; Battista, J J; Cunningham, I A

    2008-07-01

    A frequency-dependent x-ray Swank factor based on the "x-ray interaction" modulation transfer function and normalized noise power spectrum is determined from a Monte Carlo analysis. This factor was calculated in four converter materials: amorphous silicon (a-Si), amorphous selenium (a-Se), cesium iodide (CsI), and lead iodide (PbI2) for incident photon energies between 10 and 150 keV and various converter thicknesses. When scaled by the quantum efficiency, the x-ray Swank factor describes the best possible detective quantum efficiency (DQE) a detector can have. As such, this x-ray interaction DQE provides a target performance benchmark. It is expressed as a function of (Fourier-based) spatial frequency and takes into consideration signal and noise correlations introduced by reabsorption of Compton scatter and photoelectric characteristic emissions. It is shown that the x-ray Swank factor is largely insensitive to converter thickness for quantum efficiency values greater than 0.5. Thus, while most of the tabulated values correspond to thick converters with a quantum efficiency of 0.99, they are appropriate to use for many detectors in current use. A simple expression for the x-ray interaction DQE of digital detectors (including noise aliasing) is derived in terms of the quantum efficiency, x-ray Swank factor, detector element size, and fill factor. Good agreement is shown with DQE curves published by other investigators for each converter material, and the conditions required to achieve this ideal performance are discussed. For high-resolution imaging applications, the x-ray Swank factor indicates: (i) a-Si should only be used at low-energy (e.g., mammography); (ii) a-Se has the most promise for any application below 100 keV; and (iii) while quantum efficiency may be increased at energies just above the K edge in CsI and PbI2, this benefit is offset by a substantial drop in the x-ray Swank factor, particularly at high spatial frequencies. PMID:18697544

  13. Fundamental x-ray interaction limits in diagnostic imaging detectors: Frequency-dependent Swank noise

    SciTech Connect

    Hajdok, G.; Battista, J. J.; Cunningham, I. A.

    2008-07-15

    A frequency-dependent x-ray Swank factor based on the ''x-ray interaction'' modulation transfer function and normalized noise power spectrum is determined from a Monte Carlo analysis. This factor was calculated in four converter materials: amorphous silicon (a-Si), amorphous selenium (a-Se), cesium iodide (CsI), and lead iodide (PbI{sub 2}) for incident photon energies between 10 and 150 keV and various converter thicknesses. When scaled by the quantum efficiency, the x-ray Swank factor describes the best possible detective quantum efficiency (DQE) a detector can have. As such, this x-ray interaction DQE provides a target performance benchmark. It is expressed as a function of (Fourier-based) spatial frequency and takes into consideration signal and noise correlations introduced by reabsorption of Compton scatter and photoelectric characteristic emissions. It is shown that the x-ray Swank factor is largely insensitive to converter thickness for quantum efficiency values greater than 0.5. Thus, while most of the tabulated values correspond to thick converters with a quantum efficiency of 0.99, they are appropriate to use for many detectors in current use. A simple expression for the x-ray interaction DQE of digital detectors (including noise aliasing) is derived in terms of the quantum efficiency, x-ray Swank factor, detector element size, and fill factor. Good agreement is shown with DQE curves published by other investigators for each converter material, and the conditions required to achieve this ideal performance are discussed. For high-resolution imaging applications, the x-ray Swank factor indicates: (i) a-Si should only be used at low-energy (e.g., mammography); (ii) a-Se has the most promise for any application below 100 keV; and (iii) while quantum efficiency may be increased at energies just above the K edge in CsI and PbI{sub 2}, this benefit is offset by a substantial drop in the x-ray Swank factor, particularly at high spatial frequencies.

  14. A proof-of-principle study of multi-site real-time functional imaging at 3T and 7T: Implementation and validation

    PubMed Central

    Baecke, Sebastian; Lützkendorf, Ralf; Mallow, Johannes; Luchtmann, Michael; Tempelmann, Claus; Stadler, Jörg; Bernarding, Johannes

    2015-01-01

    Real-time functional Magnetic Resonance Imaging (rtfMRI) is used mainly for neurofeedback or for brain-computer interfaces (BCI). But multi-site rtfMRI could in fact help in the application of new interactive paradigms such as the monitoring of mutual information flow or the controlling of objects in shared virtual environments. For that reason, a previously developed framework that provided an integrated control and data analysis of rtfMRI experiments was extended to enable multi-site rtfMRI. Important new components included a data exchange platform for analyzing the data of both MR scanners independently and/or jointly. Information related to brain activation can be displayed separately or in a shared view. However, a signal calibration procedure had to be developed and integrated in order to permit the connecting of sites that had different hardware and to account for different inter-individual brain activation levels. The framework was successfully validated in a proof-of-principle study with twelve volunteers. Thus the overall concept, the calibration of grossly differing signals, and BCI functionality on each site proved to work as required. To model interactions between brains in real-time, more complex rules utilizing mutual activation patterns could easily be implemented to allow for new kinds of social fMRI experiments. PMID:25672521

  15. A proof-of-principle study of multi-site real-time functional imaging at 3T and 7T: Implementation and validation.

    PubMed

    Baecke, Sebastian; Lützkendorf, Ralf; Mallow, Johannes; Luchtmann, Michael; Tempelmann, Claus; Stadler, Jörg; Bernarding, Johannes

    2015-01-01

    Real-time functional Magnetic Resonance Imaging (rtfMRI) is used mainly for neurofeedback or for brain-computer interfaces (BCI). But multi-site rtfMRI could in fact help in the application of new interactive paradigms such as the monitoring of mutual information flow or the controlling of objects in shared virtual environments. For that reason, a previously developed framework that provided an integrated control and data analysis of rtfMRI experiments was extended to enable multi-site rtfMRI. Important new components included a data exchange platform for analyzing the data of both MR scanners independently and/or jointly. Information related to brain activation can be displayed separately or in a shared view. However, a signal calibration procedure had to be developed and integrated in order to permit the connecting of sites that had different hardware and to account for different inter-individual brain activation levels. The framework was successfully validated in a proof-of-principle study with twelve volunteers. Thus the overall concept, the calibration of grossly differing signals, and BCI functionality on each site proved to work as required. To model interactions between brains in real-time, more complex rules utilizing mutual activation patterns could easily be implemented to allow for new kinds of social fMRI experiments. PMID:25672521

  16. Live Imaging of Disseminated Candidiasis in Zebrafish Reveals Role of Phagocyte Oxidase in Limiting Filamentous Growth ▿ † ‡

    PubMed Central

    Brothers, Kimberly M.; Newman, Zachary R.; Wheeler, Robert T.

    2011-01-01

    Candida albicans is a human commensal and a clinically important fungal pathogen that grows in both yeast and hyphal forms during human infection. Although Candida can cause cutaneous and mucosal disease, systemic infections cause the greatest mortality in hospitals. Candidemia occurs primarily in immunocompromised patients, for whom the innate immune system plays a paramount role in immunity. We have developed a novel transparent vertebrate model of candidemia to probe the molecular nature of Candida-innate immune system interactions in an intact host. Our zebrafish infection model results in a lethal disseminated disease that shares important traits with disseminated candidiasis in mammals, including dimorphic fungal growth, dependence on hyphal growth for virulence, and dependence on the phagocyte NADPH oxidase for immunity. Dual imaging of fluorescently marked immune cells and fungi revealed that phagocytosed yeast cells can remain viable and even divide within macrophages without germinating. Similarly, although we observed apparently killed yeast cells within neutrophils, most yeast cells within these innate immune cells were viable. Exploiting this model, we combined intravital imaging with gene knockdown to show for the first time that NADPH oxidase is required for regulation of C. albicans filamentation in vivo. The transparent and easily manipulated larval zebrafish model promises to provide a unique tool for dissecting the molecular basis of phagocyte NADPH oxidase-mediated limitation of filamentous growth in vivo. PMID:21551247

  17. Spatially Resolved Plant Metabolomics: Some Potentials and Limitations of Laser-Ablation Electrospray Ionization Mass Spectrometry Metabolite Imaging1[OPEN

    PubMed Central

    Etalo, Desalegn W.; De Vos, Ric C.H.; Joosten, Matthieu H.A.J.; Hall, Robert D.

    2015-01-01

    Laser-ablation electrospray ionization (LAESI)-mass spectrometry imaging has been applied to contrasting plant organs to assess its potential as a procedure for performing in vivo metabolomics in plants. In a proof-of-concept experiment, purple/white segmented Phalaenopsis spp. petals were first analyzed using standard liquid chromatography-mass spectrometry analyses of separate extracts made specifically from the purple and white regions. Discriminatory compounds were defined and putatively annotated. LAESI analyses were then performed on living tissues, and these metabolites were then relocalized within the LAESI-generated data sets of similar tissues. Maps were made to illustrate their locations across the petals. Results revealed that, as expected, anthocyanins always mapped to the purple regions. Certain other (nonvisible) polyphenols were observed to colocalize with the anthocyanins, whereas others were found specifically within the white tissues. In a contrasting example, control and Cladosporium fulvum-infected tomato (Solanum lycopersicum) leaves were subjected to the same procedures, and it could be observed that the alkaloid tomatine has clear heterogeneous distribution across the tomato leaf lamina. Furthermore, LAESI analyses revealed perturbations in alkaloid content following pathogen infection. These results show the clear potential of LAESI-based imaging approaches as a convenient and rapid way to perform metabolomics analyses on living tissues. However, a range of limitations and factors have also been identified that must be taken into consideration when interpreting LAESI-derived data. Such aspects deserve further evaluation before this approach can be applied in a routine manner. PMID:26392264

  18. Variance-based iterative image reconstruction from few views in limited-angle C-arm computed tomography

    NASA Astrophysics Data System (ADS)

    El Hakimi, Wissam; Sakas, Georgios

    2014-03-01

    C-arm cone-beam computed tomography offers CT-like 3D imaging capabilities, but with the additional advantage of being appropriate for interventional suites. Due to the limitations of the data acquisition system, projections are oft acquired in a short scan angular range, resulting in significant artifacts, if conventional analytic formulas are applied. Furthermore, the presence of high-density objects, like metal parts, induces streak-like artifacts, which can obscure relevant anatomy. We present a new algorithm to reduce such artifacts and enhance the quality of reconstructed 3D volume. We make use of the variance of estimated voxel values over all projections to decrease the ground artifact level. The proposed algorithm is less sensitive to data truncation, and does not require explicit estimation of missing data. The number of required images is very low (up to 56 projections), which have several benefits, like significant reduction of patient dose and shortening of the acquisition time. The performance of the proposed method is demonstrated based on simulations and phantom data.

  19. Dissolved oxygen imaging in a porous medium to investigate biodegradation in a plume with limited electron acceptor supply.

    PubMed

    Huang, Wei E; Oswald, Sascha E; Lerner, David N; Smith, Colin C; Zheng, Chunmiao

    2003-05-01

    A novel combination of noninvasive imaging with an oxygen sensitive fluorescent indicator was developed to investigate the biodegradation processes occurring at the fringe of a solute plume, where the supply of oxygen was limited. A thin transparent porous matrix (156 x 120 x 3 mm) was made from quartz plates and quartz sand (212-300 microm) and enriched with acetate-degrading bacteria. A degrading plume developed from a continuous acetate source in the uniform flow field containing dissolved oxygen. Ruthenium (II)-dichlorotris(1,10-phenanthroline) (Ru(phen)3Cl2), a water-soluble fluorescent dye, was used as an indicator of dissolved oxygen. The fluorescence intensity was dependent on the concentration of oxygen because the dissolved oxygen acted as collisional quencher. The oxygen distribution was interpreted from images recorded by a CCD camera. These two-dimensional experimental results showed quantitatively how the oxygen concentrations decreased strongly at the narrow plume fringe and that oxygen was depleted at the core of the plume. Separately, dispersivity was measured in a series of nonreactive transport experiments, and biodegradation parameters were evaluated by batch experiments. Two-dimensional numerical simulations with MT3D/RT3D used these parameters, and the predicted oxygen distributions were compared with the experimental results. This measurement method provides a novel approach to investigate details of solute transport and biodegradation in porous media. PMID:12775064

  20. The traveltime holographic principle

    NASA Astrophysics Data System (ADS)

    Huang, Yunsong; Schuster, Gerard T.

    2015-01-01

    Fermat's interferometric principle is used to compute interior transmission traveltimes τpq from exterior transmission traveltimes τsp and τsq. Here, the exterior traveltimes are computed for sources s on a boundary B that encloses a volume V of interior points p and q. Once the exterior traveltimes are computed, no further ray tracing is needed to calculate the interior times τpq. Therefore this interferometric approach can be more efficient than explicitly computing interior traveltimes τpq by ray tracing. Moreover, the memory requirement of the traveltimes is reduced by one dimension, because the boundary B is of one fewer dimension than the volume V. An application of this approach is demonstrated with interbed multiple (IM) elimination. Here, the IMs in the observed data are predicted from the migration image and are subsequently removed by adaptive subtraction. This prediction is enabled by the knowledge of interior transmission traveltimes τpq computed according to Fermat's interferometric principle. We denote this principle as the `traveltime holographic principle', by analogy with the holographic principle in cosmology where information in a volume is encoded on the region's boundary.

  1. Microscopy beyond the diffraction limit using actively controlled single molecules

    PubMed Central

    MOERNER, W.E.

    2013-01-01

    Summary In this short review, the general principles are described for obtaining microscopic images with resolution beyond the optical diffraction limit with single molecules. Although it has been known for several decades that single-molecule emitters can blink or turn on and off, in recent work the addition of on/off control of molecular emission to maintain concentrations at very low levels in each imaging frame combined with sequential imaging of sparse subsets has enabled the reconstruction of images with resolution far below the optical diffraction limit. Single-molecule active control microscopy provides a powerful window into information about nanoscale structures that was previously unavailable. PMID:22582796

  2. PRINCIPLES OF SYNCHROTRON TECHNIQUES, POTENTIAL AND LIMITATIONS

    EPA Science Inventory

    Once environmental contaminants, such as arsenic, chromium, cadmium and lead, are detected, the problem becomes how to deal with them. For the past decade, researchers at the US EPA in Cincinnati have been employing synchrotron speciation methods to determine the exact chemical f...

  3. Nijboer-Zernike phase retrieval for high contrast imaging. Principle, on-sky demonstration with NACO, and perspectives in vector vortex coronagraphy

    NASA Astrophysics Data System (ADS)

    Riaud, P.; Mawet, D.; Magette, A.

    2012-09-01

    We introduce a novel phase retrieval method for astronomical applications based on the Nijboer-Zernike (NZ) theory of diffraction. We present a generalized NZ phase retrieval process that is not limited to small and symmetric aberrations and can therefore be directly applied to astronomical imaging instruments. We describe a practical demonstration of this novel method that was recently performed using data taken on-sky with NAOS-CONICA, the adaptive optics system of the Very Large Telescope. This demonstration presents the first online on-sky phase retrieval results ever obtained, and allows us to plan subsequent refinements on a well-tested basis. Among the potential refinements, and within the framework of high-contrast imaging of extra-solar planetary systems (which requires exquisite wavefront quality), we introduce an extension of the generalized NZ to the high-dynamic range case, and particularly to its use with the vector vortex coronagraph. This induces conjugated phase ramps applied to the orthogonal circular polarizations, which can be used to instantaneously retrieve the complex amplitude of the field, yielding a real-time calibration of the wavefront that does not need any other modulation such as focus or other deformable mirror probe patterns. Paper II (Riaud et al. 2012, A&A, 545, A151) presents the mathematical and practical details of the new method.

  4. Gamma-Ray Telescope and Uncertainty Principle

    ERIC Educational Resources Information Center

    Shivalingaswamy, T.; Kagali, B. A.

    2012-01-01

    Heisenberg's Uncertainty Principle is one of the important basic principles of quantum mechanics. In most of the books on quantum mechanics, this uncertainty principle is generally illustrated with the help of a gamma ray microscope, wherein neither the image formation criterion nor the lens properties are taken into account. Thus a better…

  5. Dealing with uncertainty and limited data availability at Lake Tiberias, Israel: Imaging salt diapir using hydrogeological data

    NASA Astrophysics Data System (ADS)

    Inbar, Nimrod; Rosenthal, Eliyahu; Flexer, Akiva; Möller, Peter; Siebert, Christian; Guttman, Joseph; Yellin-Dror, Annat; Magri, Fabien

    2016-04-01

    Direct data of the Tiberias Basin (TB) deep-seated stratigraphy is limited. Therefore, imaging of suspected underlying salt deposits and their structure is carried out based on salt tectonics theory and shallow seismic data interpretation. It is supported by the geochemistry of surrounding springs and numerical modeling of fluid transport processes within the basin. The Tiberias Basin (TB) is a narrow pull-apart basin located along the Dead Sea Transform. It encompasses Lake Tiberias, which is the largest fresh water lake in the Levant. Saline onshore and offshore springs and seepages are known to contribute considerable amount of salt to the lake endangering its water quality. Since the early 1980's, deep-seated salt deposits are known to exist in the Tiberias basin subsurface as a result of one deep exploration borehole. Interpretation of onshore seismic data at the southern part of the basin reveals its structure and distribution. However, offshore seismic interpretation is debatable and leads to uncertainty regarding the structure and distribution of salt deposits under the lake. The results of the current study suggest that a salt diapir rises under the lake, piercing through the basin-fill adjacent to the western boundary fault of the basin. Chemical analyses show that some springs at the western shore of the Lake contain indications of dissolved halite. In addition, numerical modeling of brine flow suggests that shallow salt domes can allow brine plumes to reach the surface and discharge along the western coast. These results allow imaging and support the hypothesis regarding the occurrences of shallow salt structures in the vicinity of the lake and contribute valuable information for sustainable management of its water.

  6. [Value and limitations of coronary artery imaging with the MRI navigator technique. Comparison with coronary angiography results in 37 patients].

    PubMed

    Haffner, C; Germain, Ph; Roul, G; Jahn, Ch; Beaujeux, R; Bareiss, P

    2002-10-01

    The introduction of a non-invasive method of imaging the coronary arteries would be a great advance in daily cardiological practice. The authors report their experience of imaging the coronary arteries with 1 Tesla MRI using the "navigator technique". Twenty-five sections 1.2 mm thick, focused on the proximal left coronary artery, were acquired with a 512 matrix, without injecting contrast during normal respiration with a tolerance on the portion of the right diaphragmatic cupola of 5 mm. Analysis of the coronary segments included in the field of view was performed on native sections after curve reconstruction and on targetedMIP series. A comparison of the results with respect to conventional coronary angiography showed a relatively limited visualisation of the proximal coronary segments because, in addition to the impossibility of carrying out the investigation in 24% of cases (faulty cardiac or respiratory synchronisation, poor signal/noise ratio), only 93% of the left main coronary and 75% of the proximal left anterior descending arteries could be visualised. In the analyzable segments, the diagnostic performances were modest with a global sensitivity of 60.8% and specificity of 91%. With the exception of the left main coronary artery, the sensitivities observed did not make MRI of the coronary arteries a rival to conventional coronary angiography. These limited performances may be explained by the lack of rapidity of the sequences of acquisition compared to the rapid motion of the structures under investigation whose dimensions are 5 to 10 times smaller than their amplitude of excursion. Technical developments are regularly accomplished in this domain, especially 3rd generation sequences in apnoea with injection of contrast media. At present, despite some results reported in the literature, angio-MRI of the coronary arteries cannot be used reliably to guide clinical decisions in coronary artery disease with the exception of some situations like congenital

  7. The study of quantum remote sensing principle prototype

    NASA Astrophysics Data System (ADS)

    Bi, Siwen; Zhang, Ying

    2015-07-01

    High signal to noise ratio and high resolution have been the goal of remote sensing. Since the classical electromagnetic wave is influenced by the diffraction limit and quantum noise limit, increasing the resolution has been close to the limit of remote sensing, In this situation, in 14 years, the author through quantum remote sensing based theory, scientific experiment and the key technology research of the three phases, before the end of December 2014 completed the study of quantum remote sensing principle prototype. Quantum remote sensing prototype is based on the theory of quantum optics, which takes manipulation, preparation and control in quantum optical field as the experimental method. Through the experiment, the results obtained are the coherent light detection imaging resolution 2-3 times. Based on a large number of experimental studies, we completed the key technology of quantum remote sensing principle prototype, scheme design and principle prototype system. Through the test, the technical indicators of the principle prototype meet the requirements, which provide technical foundation for quantum remote sensing engineering principle prototype.

  8. Passive imaging through the turbulent atmosphere - Fundamental limits on the spatial frequency resolution of a rotational shearing interferometer

    NASA Technical Reports Server (NTRS)

    Burke, J. J.; Breckinridge, J. B.

    1978-01-01

    The signal-to-noise (S/N) ratio to be expected when a 180 deg rotationally shearing interferometer is used for image recovery at the diffraction limit of a large telescope is computed. The variance and covariance of the irradiance fluctuations at the detector array are shown to yield measures of the high-frequency spatial spectrum of the source. Four fundamental sources of noise are considered: temporal fluctuations of the source, space-time fluctuations of the atmosphere, shot noise in the detected photocurrents, and the effects of finite sampling. S/N is found to be directly proportional to the angular resolution of the telescope, the single-frame integration time, the square root of the number of frames, the cube of the operating wavelength, the quantum efficiency of the detector, and the average spectral irradiance from the source on the pupil. It is inversely proportional to the cube of the field angle subtended by the source (or part thereof) under study.

  9. A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images. I. Method description

    NASA Astrophysics Data System (ADS)

    Huertas-Company, M.; Rouan, D.; Tasca, L.; Soucail, G.; Le Fèvre, O.

    2008-02-01

    Context: Morphology is the most accessible tracer of the physical structure of galaxies, but its interpretation in the framework of galaxy evolution still remains a problem. Its dependence on wavelength renders the comparison between local and high redshift populations difficult. Furthermore, the quality of the measured morphology being strongly dependent on the image resolution, the comparison between different surveys is also a problem. Aims: We present a new non-parametric method to quantify morphologies of galaxies based on a particular family of learning machines called support vector machines. The method, which can be seen as a generalization of the classical C/A classification but with an unlimited number of dimensions and non-linear boundaries between decision regions, is fully automated and thus particularly well adapted to large cosmological surveys. The source code is available for download at http://www.lesia.obspm.fr/~huertas/galsvm.html Methods: To test the method, we use a seeing limited near-infrared (Ks band, 2,16 μm) sample observed with WIRCam at CFHT at a median redshift of z ~ 0.8. The machine is trained with a simulated sample built from a local visually classified sample from the SDSS, chosen in the high-redshift sample's rest-frame (i band, 0.77 μm) and artificially redshifted to match the observing conditions. We use a 12-dimensional volume, including 5 morphological parameters, and other characteristics of galaxies such as luminosity and redshift. A fraction of the simulated sample is used to test the machine and assess its accuracy. Results: We show that a qualitative separation in two main morphological types (late type and early type) can be obtained with an error lower than 20% up to the completeness limit of the sample (KAB ~ 22), which is more than 2 times better that what would be obtained with a classical C/A classification on the same sample and indeed comparable to space data. The method is optimized to solve a specific problem

  10. A stochastic analysis of distance estimation approaches in single molecule microscopy - quantifying the resolution limits of photon-limited imaging systems

    PubMed Central

    Ram, Sripad; Ward, E. Sally; Ober, Raimund J.

    2012-01-01

    Optical microscopy is an invaluable tool to visualize biological processes at the cellular scale. In the recent past, there has been significant interest in studying these processes at the single molecule level. An important question that arises in single molecule experiments concerns the estimation of the distance of separation between two closely spaced molecules. Presently, there exists different experimental approaches to estimate the distance between two single molecules. However, it is not clear as to which of these approaches provides the best accuracy for estimating the distance. Here, we address this problem rigorously by using tools of statistical estimation theory. We derive formulations of the Fisher information matrix for the underlying estimation problem of determining the distance of separation from the acquired data for the different approaches. Through the Cramer-Rao inequality, we derive a lower bound to the accuracy with which the distance of separation can be estimated. We show through Monte-Carlo simulations that the bound can be attained by the maximum likelihood estimator. Our analysis shows that the distance estimation problem is in fact related to the localization accuracy problem, the latter being a distinct problem that deals with how accurately the location of an object can be determined. We have carried out a detailed investigation of the relationship between the Fisher information matrices of the two problems for the different experimental approaches considered here. The paper also addresses the issue of a singular Fisher information matrix, which presents a significant complication when calculating the Cramer-Rao lower bound. Here, we show how experimental design can overcome the singularity. Throughout the paper, we illustrate our results by considering a specific image profile that describe the image of a single molecule. PMID:24932067

  11. Thermal infrared properties of classical and type II Cepheids. Diffraction limited 10 μm imaging with VLT/VISIR

    NASA Astrophysics Data System (ADS)

    Gallenne, A.; Kervella, P.; Mérand, A.

    2012-02-01

    We present new thermal infrared (IR) photometry and spectral energy distributions (SEDs) of eight classical Cepheids (type I) and three type II Cepheids, using VISIR thermal IR photometric measurements, supplemented with literature data. We used the BURST mode of the instrument to get diffraction-limited images at 8.59, 11.25, and 11.85 μm. The SEDs show a IR excess at wavelengths longer than 10 μm in ten of the eleven stars. We tentatively attribute these excesses to circumstellar emission created by mass loss from the Cepheids. On the basis of some hypotheses for the dust composition, we estimate a total mass of the envelope ranging from 10-10 to 10-8 M⊙. We also detect a spatially extended emission around AX Cir, X Sgr, W Sgr, Y Oph, and U Car, while we do not resolve the circumstellar envelope (CSE) of the other stars. The averaged circumstellar envelope brightnesses relative to the stellar photosphere are α(AX Cir) = 13.8 ± 2.5%,α(X Sgr) = 7.9 ± 1.4%,α(W Sgr) = 3.8 ± 0.6%,α(Y Oph) = 15.1 ± 1.4%, and α(U Car) = 16.3 ± 1.4% at 8.59 μm. With this study, we extend the number of classical Cepheids with detected CSEs from 9 to 14, confirming that at least a large fraction of all Cepheids are experiencing significant mass loss. The presence of these CSEs may also impact the future use of Cepheids as standard candles at near and thermal infrared wavelengths. Based on observations made with ESO telescopes at Paranal observatory under program ID 081.D-0165(A).Table 2 is only available in electronic form at http://www.aanda.org

  12. Feasibility study for image reconstruction in circular digital tomosynthesis (CDTS) from limited-scan angle data based on compressed-sensing theory

    NASA Astrophysics Data System (ADS)

    Park, Yeonok; Je, Uikyu; Cho, Hyosung; Hong, Daeki; Park, Chulkyu; Cho, Heemoon; Choi, Sungil; Woo, Taeho

    2015-03-01

    In this work, we performed a feasibility study for image reconstruction in a circular digital tomosynthesis (CDTS) from limited-scan angle data based on compressed-sensing (CS) theory. Here, the X-ray source moves along an arc within a limited-scan angle (≤ 180°) on a circular path set perpendicularly to the axial direction during the image acquisition. This geometry, compared to full-angle (360°) scan geometry, allows imaging system to be designed more compactly and gives better tomographic quality than conventional linear digital tomosynthesis (DTS). We implemented an efficient CS-based reconstruction algorithm for the proposed geometry and performed systematic simulations to investigate the image characteristics. We successfully reconstructed CDTS images with incomplete projections acquired at several selected limited-scan angles of 45°, 90°, 135°, and 180° for a given tomographic angle of 80° and evaluated the reconstruction quality. Our simulation results indicate that the proposed method can provide superior tomographic quality for axial view and even for the other views (i.e., sagittal and coronal), as in computed tomography, to conventional DTS.

  13. Basic design principles of colorimetric vision systems

    NASA Astrophysics Data System (ADS)

    Mumzhiu, Alex M.

    1998-10-01

    Color measurement is an important part of overall production quality control in textile, coating, plastics, food, paper and other industries. The color measurement instruments such as colorimeters and spectrophotometers, used for production quality control have many limitations. In many applications they cannot be used for a variety of reasons and have to be replaced with human operators. Machine vision has great potential for color measurement. The components for color machine vision systems, such as broadcast quality 3-CCD cameras, fast and inexpensive PCI frame grabbers, and sophisticated image processing software packages are available. However the machine vision industry has only started to approach the color domain. The few color machine vision systems on the market, produced by the largest machine vision manufacturers have very limited capabilities. A lack of understanding that a vision based color measurement system could fail if it ignores the basic principles of colorimetry is the main reason for the slow progress of color vision systems. the purpose of this paper is to clarify how color measurement principles have to be applied to vision systems and how the electro-optical design features of colorimeters have to be modified in order to implement them for vision systems. The subject of this presentation far exceeds the limitations of a journal paper so only the most important aspects will be discussed. An overview of the major areas of applications for colorimetric vision system will be discussed. Finally, the reasons why some customers are happy with their vision systems and some are not will be analyzed.

  14. An innovative technique for contrast enhancement of computed tomography images using normalized gamma-corrected contrast-limited adaptive histogram equalization

    NASA Astrophysics Data System (ADS)

    Al-Ameen, Zohair; Sulong, Ghazali; Rehman, Amjad; Al-Dhelaan, Abdullah; Saba, Tanzila; Al-Rodhaan, Mznah

    2015-12-01

    Image contrast is an essential visual feature that determines whether an image is of good quality. In computed tomography (CT), captured images tend to be low contrast, which is a prevalent artifact that reduces the image quality and hampers the process of extracting its useful information. A common tactic to process such artifact is by using histogram-based techniques. However, although these techniques may improve the contrast for different grayscale imaging applications, the results are mostly unacceptable for CT images due to the presentation of various faults, noise amplification, excess brightness, and imperfect contrast. Therefore, an ameliorated version of the contrast-limited adaptive histogram equalization (CLAHE) is introduced in this article to provide a good brightness with decent contrast for CT images. The novel modification to the aforesaid technique is done by adding an initial phase of a normalized gamma correction function that helps in adjusting the gamma of the processed image to avoid the common errors of the basic CLAHE of the excess brightness and imperfect contrast it produces. The newly developed technique is tested with synthetic and real-degraded low-contrast CT images, in which it highly contributed in producing better quality results. Moreover, a low intricacy technique for contrast enhancement is proposed, and its performance is also exhibited against various versions of histogram-based enhancement technique using three advanced image quality assessment metrics of Universal Image Quality Index (UIQI), Structural Similarity Index (SSIM), and Feature Similarity Index (FSIM). Finally, the proposed technique provided acceptable results with no visible artifacts and outperformed all the comparable techniques.

  15. Principles of Natural Photosynthesis.

    PubMed

    Krewald, Vera; Retegan, Marius; Pantazis, Dimitrios A

    2016-01-01

    Nature relies on a unique and intricate biochemical setup to achieve sunlight-driven water splitting. Combined experimental and computational efforts have produced significant insights into the structural and functional principles governing the operation of the water-oxidizing enzyme Photosystem II in general, and of the oxygen-evolving manganese-calcium cluster at its active site in particular. Here we review the most important aspects of biological water oxidation, emphasizing current knowledge on the organization of the enzyme, the geometric and electronic structure of the catalyst, and the role of calcium and chloride cofactors. The combination of recent experimental work on the identification of possible substrate sites with computational modeling have considerably limited the possible mechanistic pathways for the critical O-O bond formation step. Taken together, the key features and principles of natural photosynthesis may serve as inspiration for the design, development, and implementation of artificial systems. PMID:26099285

  16. Equivalence Principle and Gravitational Redshift

    SciTech Connect

    Hohensee, Michael A.; Chu, Steven; Mueller, Holger; Peters, Achim

    2011-04-15

    We investigate leading order deviations from general relativity that violate the Einstein equivalence principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter-wave, microwave, optical, and Moessbauer clock tests, yields comprehensive limits on spin-independent Einstein equivalence principle-violating standard model extension terms at the 10{sup -6} level.

  17. Evaluation of state-of-the-art imaging systems for in vivo monitoring of retinal structure in mice: current capabilities and limitations

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Zam, Azhar; Pugh, Edward N.; Zawadzki, Robert J.

    2014-02-01

    Animal models of human diseases play an important role in studying and advancing our understanding of these conditions, allowing molecular level studies of pathogenesis as well as testing of new therapies. Recently several non-invasive imaging modalities including Fundus Camera, Scanning Laser Ophthalmoscopy (SLO) and Optical Coherence Tomography (OCT) have been successfully applied to monitor changes in the retinas of the living animals in experiments in which a single animal is followed over a portion of its lifespan. Here we evaluate the capabilities and limitations of these three imaging modalities for visualization of specific structures in the mouse eye. Example images acquired from different types of mice are presented. Future directions of development for these instruments and potential advantages of multi-modal imaging systems are discussed as well.

  18. Principle Paradigms Revisiting the Dublin Core 1:1 Principle

    ERIC Educational Resources Information Center

    Urban, Richard J.

    2012-01-01

    The Dublin Core "1:1 Principle" asserts that "related but conceptually different entities, for example a painting and a digital image of the painting, are described by separate metadata records" (Woodley et al., 2005). While this seems to be a simple requirement, studies of metadata quality have found that cultural heritage…

  19. Quantum measurements and Landauer's principle

    NASA Astrophysics Data System (ADS)

    Shevchenko, V.

    2015-05-01

    Information processing systems must obey laws of physics. One of particular examples of this general statement is known as Landauer's principle - irreversible operations (such as erasure) performed by any computing device at finite temperature have to dissipate some amount of heat bound from below. Together with other results of this kind, Landauer's principle represents a fundamental limit any modern or future computer must obey. We discuss interpretation of the physics behind the Landauer's principle using a model of Unruh-DeWitt detector. Of particular interest is the validity of this limit in quantum domain. We systematically study finite time effects. It is shown, in particular, that in high temperature limit finiteness of measurement time leads to renormalization of the detector's temperature.

  20. High-quality imaging in environmental scanning electron microscopy - optimizing the pressure limiting system and the secondary electron detection of a commercially available ESEM.

    PubMed

    Fitzek, H; Schroettner, H; Wagner, J; Hofer, F; Rattenberger, J

    2016-04-01

    In environmental scanning electron microscopy applications in the kPa regime are of increasing interest for the investigation of wet and biological samples, because neither sample preparation nor extensive cooling are necessary. Unfortunately, the applications are limited by poor image quality. In this work the image quality at high pressures of a FEI Quanta 600 (field emission gun) and a FEI Quanta 200 (thermionic gun) is greatly improved by optimizing the pressure limiting system and the secondary electron (SE) detection system. The scattering of the primary electron beam strongly increases with pressure and thus the image quality vanishes. The key to high-image quality at high pressures is to reduce scattering as far as possible while maintaining ideal operation conditions for the SE-detector. The amount of scattering is reduced by reducing both the additional stagnation gas thickness (aSGT) and the environmental distance (ED). A new aperture holder is presented that significantly reduces the aSGT while maintaining the same field-of-view (FOV) as the original design. With this aperture holder it is also possible to make the aSGT even smaller at the expense of a smaller FOV. A new blade-shaped SE-detector is presented yielding better image quality than usual flat SE-detectors. The electrode of the new SE detector is positioned on the sample table, which allows the SE-detector to operate at ideal conditions regardless of pressure and ED. PMID:26540292

  1. Dental cone-beam CT reconstruction from limited-angle view data based on compressed-sensing (CS) theory for fast, low-dose X-ray imaging

    NASA Astrophysics Data System (ADS)

    Je, Uikyu; Cho, Hyosung; Lee, Minsik; Oh, Jieun; Park, Yeonok; Hong, Daeki; Park, Cheulkyu; Cho, Heemoon; Choi, Sungil; Koo, Yangseo

    2014-06-01

    Recently, reducing radiation doses has become an issue of critical importance in the broader radiological community. As a possible technical approach, especially, in dental cone-beam computed tomography (CBCT), reconstruction from limited-angle view data (< 360°) would enable fast scanning with reduced doses to the patient. In this study, we investigated and implemented an efficient reconstruction algorithm based on compressed-sensing (CS) theory for the scan geometry and performed systematic simulation works to investigate the image characteristics. We also performed experimental works by applying the algorithm to a commercially-available dental CBCT system to demonstrate its effectiveness for image reconstruction in incomplete data problems. We successfully reconstructed CBCT images with incomplete projections acquired at selected scan angles of 120, 150, 180, and 200° with a fixed angle step of 1.2° and evaluated the reconstruction quality quantitatively. Both simulation and experimental demonstrations of the CS-based reconstruction from limited-angle view data show that the algorithm can be applied directly to current dental CBCT systems for reducing the imaging doses and further improving the image quality.

  2. Principles and practice of sonography

    SciTech Connect

    Fleischer, A.C.; James, A.E.

    1987-01-01

    This book is a text of sonographic technique, emphasizing clinical and diagnostic procedures. Ultrasound images and explanatory line drawings are placed side-by-side to facilitate interpretation. This book covers instrumentation and scanning principles, obstetric, gynecologic, abdominal, renal and urologic, pediatric, plus superficial structure sonography.

  3. An efficient reconstruction algorithm for differential phase-contrast tomographic images from a limited number of views

    SciTech Connect

    Sunaguchi, Naoki; Yuasa, Tetsuya; Gupta, Rajiv; Ando, Masami

    2015-12-21

    The main focus of this paper is reconstruction of tomographic phase-contrast image from a set of projections. We propose an efficient reconstruction algorithm for differential phase-contrast computed tomography that can considerably reduce the number of projections required for reconstruction. The key result underlying this research is a projection theorem that states that the second derivative of the projection set is linearly related to the Laplacian of the tomographic image. The proposed algorithm first reconstructs the Laplacian image of the phase-shift distribution from the second-derivative of the projections using total variation regularization. The second step is to obtain the phase-shift distribution by solving a Poisson equation whose source is the Laplacian image previously reconstructed under the Dirichlet condition. We demonstrate the efficacy of this algorithm using both synthetically generated simulation data and projection data acquired experimentally at a synchrotron. The experimental phase data were acquired from a human coronary artery specimen using dark-field-imaging optics pioneered by our group. Our results demonstrate that the proposed algorithm can reduce the number of projections to approximately 33% as compared with the conventional filtered backprojection method, without any detrimental effect on the image quality.

  4. Equivalence principles and electromagnetism

    NASA Technical Reports Server (NTRS)

    Ni, W.-T.

    1977-01-01

    The implications of the weak equivalence principles are investigated in detail for electromagnetic systems in a general framework. In particular, it is shown that the universality of free-fall trajectories (Galileo weak equivalence principle) does not imply the validity of the Einstein equivalence principle. However, the Galileo principle plus the universality of free-fall rotation states does imply the Einstein principle.

  5. Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra.

    PubMed

    Takegami, Kazuki; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi; Maehata, Itsumi; Kanazawa, Yuki; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

    2016-07-01

    Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1-20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector. Then, with the following two experimental settings, corresponding X-ray spectra were measured with 40-120 kVp and 0.5-1000 mAs at a source-to-detector distance of 100 cm: (1) X-rays penetrating a soft-tissue-equivalent phantom with the OSL dosimeter attached directly on the phantom, and (2) X-rays penetrating only the soft-tissue-equivalent phantom. Next, the energy fluence and errors in the fluence were calculated from the spectra. When the energy fluence with errors concerning these two experimental conditions was estimated to be indistinctive, we defined the condition as the OSL dosimeter not being identified on the X-ray image. Based on our analysis, we determined the identification limit of the dosimeter. We then compared our results with those for the general irradiation conditions used in clinics. We found that the OSL dosimeter could not be identified under the irradiation conditions of abdominal and chest radiography, namely, one can apply the OSL dosimeter to measurement of the exposure dose in the irradiation field of X-rays without disturbing medical images. PMID:27260346

  6. Band-limited image plane masks for the Terrestrial Planet Finder coronagraph: materials and designs for broadband performance

    NASA Astrophysics Data System (ADS)

    Balasubramanian, Kunjithapatham

    2008-01-01

    Coronagraphs for detection and characterization of exosolar earthlike planets require accurate masks with broadband performance in the visible and near infrared spectrum. Design and fabrication of image plane masks capable of suppressing broadband starlight to 10-10 level contrast presents technical challenges. We discuss basic approaches, material choices, designs, and fabrication options for image plane masks with particular focus on material properties to obtain adequate spectral performance. Based on theoretical analysis, we show that metals such as Pt and Ni, and alloys such as Inconel, may be employed as promising mask materials that can meet broadband performance requirements.

  7. A psychovisual quality metric in free-energy principle.

    PubMed

    Zhai, Guangtao; Wu, Xiaolin; Yang, Xiaokang; Lin, Weisi; Zhang, Wenjun

    2012-01-01

    In this paper, we propose a new psychovisual quality metric of images based on recent developments in brain theory and neuroscience, particularly the free-energy principle. The perception and understanding of an image is modeled as an active inference process, in which the brain tries to explain the scene using an internal generative model. The psychovisual quality is thus closely related to how accurately visual sensory data can be explained by the generative model, and the upper bound of the discrepancy between the image signal and its best internal description is given by the free energy of the cognition process. Therefore, the perceptual quality of an image can be quantified using the free energy. Constructively, we develop a reduced-reference free-energy-based distortion metric (FEDM) and a no-reference free-energy-based quality metric (NFEQM). The FEDM and the NFEQM are nearly invariant to many global systematic deviations in geometry and illumination that hardly affect visual quality, for which existing image quality metrics wrongly predict severe quality degradation. Although with very limited or even without information on the reference image, the FEDM and the NFEQM are highly competitive compared with the full-reference SSIM image quality metric on images in the popular LIVE database. Moreover, FEDM and NFEQM can measure correctly the visual quality of some model-based image processing algorithms, for which the competing metrics often contradict with viewers' opinions. PMID:21724508

  8. Multi-frequency subspace migration for imaging of perfectly conducting, arc-like cracks in full- and limited-view inverse scattering problems

    NASA Astrophysics Data System (ADS)

    Park, Won-Kwang

    2015-02-01

    Multi-frequency subspace migration imaging techniques are usually adopted for the non-iterative imaging of unknown electromagnetic targets, such as cracks in concrete walls or bridges and anti-personnel mines in the ground, in the inverse scattering problems. It is confirmed that this technique is very fast, effective, robust, and can not only be applied to full- but also to limited-view inverse problems if a suitable number of incidents and corresponding scattered fields are applied and collected. However, in many works, the application of such techniques is heuristic. With the motivation of such heuristic application, this study analyzes the structure of the imaging functional employed in the subspace migration imaging technique in two-dimensional full- and limited-view inverse scattering problems when the unknown targets are arbitrary-shaped, arc-like perfectly conducting cracks located in the two-dimensional homogeneous space. In contrast to the statistical approach based on statistical hypothesis testing, our approach is based on the fact that the subspace migration imaging functional can be expressed by a linear combination of the Bessel functions of integer order of the first kind. This is based on the structure of the Multi-Static Response (MSR) matrix collected in the far-field at nonzero frequency in either Transverse Magnetic (TM) mode (Dirichlet boundary condition) or Transverse Electric (TE) mode (Neumann boundary condition). The investigation of the expression of imaging functionals gives us certain properties of subspace migration and explains why multi-frequency enhances imaging resolution. In particular, we carefully analyze the subspace migration and confirm some properties of imaging when a small number of incident fields are applied. Consequently, we introduce a weighted multi-frequency imaging functional and confirm that it is an improved version of subspace migration in TM mode. Various results of numerical simulations performed on the far

  9. Image-based surface reconstruction in geomorphometry - merits, limits and developments of a promising tool for geoscientists

    NASA Astrophysics Data System (ADS)

    Eltner, A.; Kaiser, A.; Castillo, C.; Rock, G.; Neugirg, F.; Abellan, A.

    2015-12-01

    Photogrammetry and geosciences are closely linked since the late 19th century. Today, a wide range of commercial and open-source software enable non-experts users to obtain high-quality 3-D datasets of the environment, which was formerly reserved to remote sensing experts, geodesists or owners of cost-intensive metric airborne imaging systems. Complex tridimensional geomorphological features can be easily reconstructed from images captured with consumer grade cameras. Furthermore, rapid developments in UAV technology allow for high quality aerial surveying and orthophotography generation at a relatively low-cost. The increasing computing capacities during the last decade, together with the development of high-performance digital sensors and the important software innovations developed by other fields of research (e.g. computer vision and visual perception) has extended the rigorous processing of stereoscopic image data to a 3-D point cloud generation from a series of non-calibrated images. Structure from motion methods offer algorithms, e.g. robust feature detectors like the scale-invariant feature transform for 2-D imagery, which allow for efficient and automatic orientation of large image sets without further data acquisition information. Nevertheless, the importance of carrying out correct fieldwork strategies, using proper camera settings, ground control points and ground truth for understanding the different sources of errors still need to be adapted in the common scientific practice. This review manuscript intends not only to summarize the present state of published research on structure-from-motion photogrammetry applications in geomorphometry, but also to give an overview of terms and fields of application, to quantify already achieved accuracies and used scales using different strategies, to evaluate possible stagnations of current developments and to identify key future challenges. It is our belief that the identification of common errors, "bad practices

  10. Imaging the ruptures of the 2009 Samoan and Sumatran earthquakes using broadband network back-projections: Results and limitations

    NASA Astrophysics Data System (ADS)

    Hutko, A. R.; Lay, T.; Koper, K. D.

    2009-12-01

    Applications of teleseismic P-wave back-projection to image gross characteristics of large earthquake finite-source ruptures have been enabled by ready availability of large digital data sets. Imaging with short-period data from dense arrays or broadband data from global networks can place constraints on rupture attributes that otherwise have to be treated parametrically in conventional modeling and inversion procedures. Back-projection imaging may constrain choice of fault plane and rupture direction, velocity, duration and length for large (M>~8.0) earthquakes, and can robustly locate early aftershocks embedded in mainshock surface waves. Back-projection methods seek locations of coherent energy release from the source region, ideally associated with down-going P wave energy. For shallow events, depth phase arrivals can produce artifacts in back-projection images that appear as secondary or even prominent features with incorrect apparent source locations and times, and such effects need to be recognized. We apply broadband P-wave back-projection imaging to the 29 September 2009 Samoa (Mw8.2) and 30 September 2009 Sumatra (Mw7.6) earthquakes using data from globally distributed broadband stations and compare results to back-projections of synthetic seismograms from finite-source models for these events to evaluate the artifacts from depth phases. Back-projection images for the great normal-faulting Samoa event feature two prominent bright spots, which could be interpreted to correspond to two distinct slip patches, one near the epicenter in the outer trench slope and the other approximately 80 km to the west near the plate boundary megathrust where many aftershocks occurred. This interpretation is at odds with finite-fault modeling results, which indicate a predominantly bilateral rupture in the NW-SE direction on a steeply dipping trench slope fault, with rupture extending about 60 km in each direction. Back-projections of data and synthetic seismograms from the

  11. Basic Principles in Oncology

    NASA Astrophysics Data System (ADS)

    Vogl, Thomas J.

    The evolving field of interventional oncology can only be considered as a small integrative part in the complex area of oncology. The new field of interventional oncology needs a standardization of the procedures, the terminology, and criteria to facilitate the effective communication of ideas and appropriate comparison between treatments and new integrative technology. In principle, ablative therapy is a part of locoregional oncological therapy and is defined either as chemical ablation using ethanol or acetic acid, or thermotherapies such as radiofrequency, laser, microwave, and cryoablation. All these new evolving therapies have to be exactly evaluated and an adequate terminology has to be used to define imaging findings and pathology. All the different technologies and evaluated therapies have to be compared, and the results have to be analyzed in order to improve the patient outcome.

  12. Neuronavigation. Principles. Surgical technique.

    PubMed

    Ivanov, Marcel; Ciurea, Alexandru Vlad

    2009-01-01

    Neuronavigation and stereotaxy are techniques designed to help neurosurgeons precisely localize different intracerebral pathological processes by using a set of preoperative images (CT, MRI, fMRI, PET, SPECT etc.). The development of computer assisted surgery was possible only after a significant technological progress, especially in the area of informatics and imagistics. The main indications of neuronavigation are represented by the targeting of small and deep intracerebral lesions and choosing the best way to treat them, in order to preserve the neurological function. Stereotaxis also allows lesioning or stimulation of basal ganglia for the treatment of movement disorders. These techniques can bring an important amount of confort both to the patient and to the neurosurgeon. Neuronavigation was introduced in Romania around 2003, in four neurosurgical centers. We present our five-years experience in neuronavigation and describe the main principles and surgical techniques. PMID:20108488

  13. Pushing the Optical Imaging Limits of Cancer with Multi-Frequency-Band Raster-Scan Optoacoustic Mesoscopy (RSOM)

    PubMed Central

    Omar, Murad; Schwarz, Mathias; Soliman, Dominik; Symvoulidis, Panagiotis; Ntziachristos, Vasilis

    2015-01-01

    Angiogenesis is a central cancer hallmark, necessary for supporting tumor growth and metastasis. In vivo imaging of angiogenesis is commonly applied, to understand dynamic processes in cancer development and treatment strategies. However, most radiological modalities today assess angiogenesis based on indirect mechanisms, such as the rate of contrast enhancement after contrast agent administration. We studied the performance of raster-scan optoacoustic mesoscopy (RSOM), to directly reveal the vascular network supporting melanoma growth in vivo, at 50 MHz and 100 MHz, through several millimeters of tumor depth. After comparing the performance at each frequency, we recorded, for the first time, high-resolution images of melanin tumor vasculature development in vivo, over a period of several days. Image validation was provided by means of cryo-slice sections of the same tumor after sacrificing the mice. We show how optoacoustic (photoacoustic) mesoscopy reveals a potentially powerful look into tumor angiogenesis, with properties and features that are markedly different than other radiological modalities. This will facilitate a better understanding of tumor’s angiogenesis, and the evaluation of treatment strategies. PMID:25748240

  14. Single-Step 3-D Image Reconstruction in Magnetic Induction Tomography: Theoretical Limits of Spatial Resolution and Contrast to Noise Ratio

    PubMed Central

    Hollaus, Karl; Rosell-Ferrer, Javier; Merwa, Robert

    2006-01-01

    Magnetic induction tomography (MIT) is a low-resolution imaging modality for reconstructing the changes of the complex conductivity in an object. MIT is based on determining the perturbation of an alternating magnetic field, which is coupled from several excitation coils to the object. The conductivity distribution is reconstructed from the corresponding voltage changes induced in several receiver coils. Potential medical applications comprise the continuous, non-invasive monitoring of tissue alterations which are reflected in the change of the conductivity, e.g. edema, ventilation disorders, wound healing and ischemic processes. MIT requires the solution of an ill-posed inverse eddy current problem. A linearized version of this problem was solved for 16 excitation coils and 32 receiver coils with a model of two spherical perturbations within a cylindrical phantom. The method was tested with simulated measurement data. Images were reconstructed with a regularized single-step Gauss–Newton approach. Theoretical limits for spatial resolution and contrast/noise ratio were calculated and compared with the empirical results from a Monte-Carlo study. The conductivity perturbations inside a homogeneous cylinder were localized for a SNR between 44 and 64 dB. The results prove the feasibility of difference imaging with MIT and give some quantitative data on the limitations of the method. PMID:17031597

  15. Radiation protection principles of NCRP.

    PubMed

    Kase, Kenneth R

    2004-09-01

    The current recommendations of the National Council on Radiation Protection and Measurements (NCRP) relative to ionizing radiation are based on radiation protection principles that developed historically as information about radiation effects on human populations became available. Because the NCRP Charter states that the NCRP will cooperate with the International Commission on Radiological Protection (ICRP), the basic principles and recommendations for radiation protection of the NCRP are closely coupled with those of the ICRP. Thus, the fundamental principles of justification, optimization, and dose limitation as initially stated in ICRP Publication 26 have been adopted and applied by the NCRP in its recommendations. ICRP and NCRP recommendations on dose limitation for the general public and for occupationally exposed individuals are based on the same analyses of radiation risk, and, while similar, there are differences reflecting the aspects of radiation application and exposure circumstances unique to the United States. The NCRP has recently extended its guidance to address exposure to individuals engaged in space activities. Several reports have been issued or are in preparation to provide recommendations on dose limitation and the development of radiation safety programs to apply the radiation protection principles in space activities. The biological basis for these recommendations is provided in these and accompanying NCRP reports. Recommendations for the application of basic radiation protection principles have been made in many reports over the years. Those that are most current appear in approximately 50 reports published in the last 15 y. These address radiation safety practices in industrial and medical institutions, control of radionuclides in the environment, protection of the public, and assessment of radiation risk. Some of the aspects of these recommendations will be discussed. Current recommendations related to radiation safety practice are based

  16. Principles of immunology.

    PubMed

    Lentz, Ashley K; Feezor, Robert J

    2003-12-01

    The immune system, composed of innate and acquired immunity, allows an organism to fight off foreign pathogens. Healthy immunity accomplishes four essential principles: (1) ability to detect and fight off infection; (2) ability to recognize a host's own cells as "self," thereby protecting them from attack; (3) a memory from previous foreign infections; and (4) ability to limit the response after the pathogen has been removed. In an unaltered state, the intricate network of immunologic organs and cells creates an environment for proper host defense. Without adequate execution of immunologic mechanisms, a host is rendered defenseless against pathogens. Conversely, an unchecked immune response can be self-destructive. As a result of either of these untoward sequelae, immune dysfunction can elicit disease states in the host. The goal of this review is to elucidate the characteristics of a healthy immune system, focusing on the principles of immunity and the cells that participate in host protection. We also briefly discuss the clinical ramifications of immune dysfunction. PMID:16215081

  17. Fracture mechanics principles.

    PubMed

    Mecholsky, J J

    1995-03-01

    The principles of linear elastic fracture mechanics (LEFM) were developed in the 1950s by George Irwin (1957). This work was based on previous investigations of Griffith (1920) and Orowan (1944). Irwin (1957) demonstrated that a crack shape in a particular location with respect to the loading geometry had a stress intensity associated with it. He also demonstrated the equivalence between the stress intensity concept and the familiar Griffith criterion of failure. More importantly, he described the systematic and controlled evaluation of the toughness of a material. Toughness is defined as the resistance of a material to rapid crack propagation and can be characterized by one parameter, Kic. In contrast, the strength of a material is dependent on the size of the initiating crack present in that particular sample or component. The fracture toughness of a material is generally independent of the size of the initiating crack. The strength of any product is limited by the size of the cracks or defects during processing, production and handling. Thus, the application of fracture mechanics principles to dental biomaterials is invaluable in new material development, production control and failure analysis. This paper describes the most useful equations of fracture mechanics to be used in the failure analysis of dental biomaterials. PMID:8621030

  18. Three basic principles of success.

    PubMed

    Levin, Roger

    2003-06-01

    Basic business principles all but ensure success when they are followed consistently. Putting strategies, objectives and tactics in place is the first step toward being able to document systems, initiate scripting and improve staff training. Without the basic steps, systems, scripting and training the practice for performance would be hit or miss, at best. More importantly, applying business principles ensures that limited practice resources are dedicated to the achievement of the strategy. By following this simple, three-step process, a dental practice can significantly enhance both financial success and dentist and staff satisfaction. PMID:12839415

  19. Principle of least wave change.

    PubMed

    Abramson, N

    1989-05-01

    Fermat's principle of least time has some well-known limitations. It does not, for example, apply to diffraction gratings and holograms, because it does not include the concept of waves. The substitution of least number of waves in flight for least time of flight and the addition of a term that is a function of the grating frequency result in a generalized principle. It is easy to remember because it is based on only the number of waves minus the number of grooves, and it would be especially useful when refraction and diffraction are combined, as, for example, in some holographic optical elements. PMID:2723846

  20. Limits to Inclusion

    ERIC Educational Resources Information Center

    Hansen, Janne Hedegaard

    2012-01-01

    In this article, I will argue that a theoretical identification of the limit to inclusion is needed in the conceptual identification of inclusion. On the one hand, inclusion is formulated as a vision that is, in principle, limitless. On the other hand, there seems to be an agreement that inclusion has a limit in the pedagogical practice. However,…

  1. Influence of temporal noise on the skin blood flow measurements performed by cooled thermal imaging camera: limit possibilities within each physiological frequency range

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Volkov, I. U.; Fomin, A. V.

    2016-04-01

    This paper describes limit possibilities of modern cooled thermal imaging cameras as a tool for estimation of blood flow oscillations at the surface of living body. Skin temperature oscillations, as we assumed, are a consequence of the blood flow oscillations. We considered the temperature sensitivity 0.01-0.02 °C as a typical for the most of modern cooled long wave thermal imaging cameras. Fourier filter used to investigate the temperature signal separately within endothelial, neurogenic, myogenic, respiratory and cardiac frequency ranges. The level of temporal noise has been estimated during measurements of no living body with stabilized temperature ~ 24°C. The level of temperature oscillations has been calculated for the group of healthy subjects within each frequency range. Thus, we were able to determine signal-to-noise ratio within frequency band [0.001, 1] Hz. As a result, we determine that skin temperature oscillations measured by thermal imaging camera with sensitivity 0.02°C have the upper frequency limit ~ 0.2 Hz. In other words, within the respiratory and cardiac frequency ranges of blood flow oscillations the noise level exceeds signal one, and temperature measurements at the skin surface are practically useless. The endothelial, neurogenic and myogenic components of the temperature oscillations contain ~98% of the total spectral power of the signal. We have plot the empirical extrapolated curve of sensitivity of thermal imaging camera vs. frequency of the temperature oscillations. The data analysis shows that measurements of skin temperature oscillations within respiratory and cardiac ranges require the temperature sensitivity at least ~ 0.01°C and 0.001°C, respectively.

  2. Synchrotron X-ray Imaging via Ultra-small-angle Scattering: Principles of Quantitative Analysis and Application in Studyingbone Integration to Synthetic Grafting Materials

    SciTech Connect

    Morelhao, S.; Coelho, P; Honnicke, M

    2010-01-01

    Optimized experimental conditions for extracting accurate information at subpixel length scales from analyzer-based X-ray imaging were obtained and applied to investigate bone regeneration by means of synthetic {beta}-TCP grafting materials in a rat calvaria model. The results showed a 30% growth in the particulate size due to bone ongrowth/ingrowth within the critical size defect over a 1-month healing period.

  3. Interferometry based multispectral photon-limited 2D and 3D integral image encryption employing the Hartley transform.

    PubMed

    Muniraj, Inbarasan; Guo, Changliang; Lee, Byung-Geun; Sheridan, John T

    2015-06-15

    We present a method of securing multispectral 3D photon-counted integral imaging (PCII) using classical Hartley Transform (HT) based encryption by employing optical interferometry. This method has the simultaneous advantages of minimizing complexity by eliminating the need for holography recording and addresses the phase sensitivity problem encountered when using digital cameras. These together with single-channel multispectral 3D data compactness, the inherent properties of the classical photon counting detection model, i.e. sparse sensing and the capability for nonlinear transformation, permits better authentication of the retrieved 3D scene at various depth cues. Furthermore, the proposed technique works for both spatially and temporally incoherent illumination. To validate the proposed technique simulations were carried out for both the 2D and 3D cases. Experimental data is processed and the results support the feasibility of the encryption method. PMID:26193568

  4. Overcoming x-ray tube small focal spot output limitations for high resolution region of interest imaging

    NASA Astrophysics Data System (ADS)

    Gupta, Sandesh K.; Jain, Amit; Bednarek, Daniel R.; Rudin, Stephen

    2012-03-01

    We investigate methods to increase x-ray tube output to enable improved quantum image quality with a higher generalized-NEQ (GNEQ) while maintaining a small focal-spot size for the new high-resolution Micro-angiographic Fluoroscope (MAF) Region of Interest (ROI) imaging system. Rather than using a larger focal spot to increase tubeloading capacity with degraded resolution, we evaluated separately or in combination three methods to increase tube output: 1) reducing the anode angle and lengthening the filament to maintain a constant effective small focal-spot size, 2) using the standard medium focal spot viewed from a direction on the anode side of the field and 3) increasing the frame rate (frames/second) in combination with temporal filter. The GNEQ was compared for the MAF for the small focal-spot at the central axis, and for the medium focal-spot with a higher output on the anode side as well as for the small focal spot with different temporal recursive filtering weights. A net output increase of about 4.0 times could be achieved with a 2-degree anode angle (without the added filtration) and a 4 times longer filament compared to that of the standard 8-degree target. The GNEQ was also increased for the medium focal-spot due to its higher output capacity and for the temporally filtered higher frame rate. Thus higher tube output, while maintaining a small effective focal-spot, should be achievable using one or more of the three methods described with only small modifications of standard x-ray tube geometry.

  5. Monte Carlo simulation of a quantum noise limited Čerenkov detector based on air-spaced light guiding taper for megavoltage x-ray imaging

    SciTech Connect

    Teymurazyan, A.; Rowlands, J. A.; Pang, G.

    2014-04-15

    Purpose: Electronic Portal Imaging Devices (EPIDs) have been widely used in radiation therapy and are still needed on linear accelerators (Linacs) equipped with kilovoltage cone beam CT (kV-CBCT) or MRI systems. Our aim is to develop a new high quantum efficiency (QE) Čerenkov Portal Imaging Device (CPID) that is quantum noise limited at dose levels corresponding to a single Linac pulse. Methods: Recently a new concept of CPID for MV x-ray imaging in radiation therapy was introduced. It relies on Čerenkov effect for x-ray detection. The proposed design consisted of a matrix of optical fibers aligned with the incident x-rays and coupled to an active matrix flat panel imager (AMFPI) for image readout. A weakness of such design is that too few Čerenkov light photons reach the AMFPI for each incident x-ray and an AMFPI with an avalanche gain is required in order to overcome the readout noise for portal imaging application. In this work the authors propose to replace the optical fibers in the CPID with light guides without a cladding layer that are suspended in air. The air between the light guides takes on the role of the cladding layer found in a regular optical fiber. Since air has a significantly lower refractive index (∼1 versus 1.38 in a typical cladding layer), a much superior light collection efficiency is achieved. Results: A Monte Carlo simulation of the new design has been conducted to investigate its feasibility. Detector quantities such as quantum efficiency (QE), spatial resolution (MTF), and frequency dependent detective quantum efficiency (DQE) have been evaluated. The detector signal and the quantum noise have been compared to the readout noise. Conclusions: Our studies show that the modified new CPID has a QE and DQE more than an order of magnitude greater than that of current clinical systems and yet a spatial resolution similar to that of current low-QE flat-panel based EPIDs. Furthermore it was demonstrated that the new CPID does not require an

  6. Evidence of water limited affects in tree density in a subalpine/alpine environment as inferred from hyperspatial image data and climate gradient analysis

    NASA Astrophysics Data System (ADS)

    Greenberg, J. A.; Vanderbilt, V. C.; Dobrowski, S. Z.

    2005-12-01

    We investigated the probability of a tree to establish, grow and survive, independent of species, in a topographically heterogeneous landscape along the eastern side of the Lake Tahoe Basin, NV. The goal was to determine if direct and indirect gradients, all derived from a digital elevation model (DEM), could be used to infer which abiotic variable(s) relate to tree density. We used a relatively new suite of analysis tools and technologies that can identify and describe each tree in a hyperspatial image (ground resolution smaller than the object(s) of interest; in our case, a tree). We generated continuous individual tree maps across the entire eastern side of the Lake Tahoe basin, which completely circumvents ground-based sampling and scaling issues. We found the expected pattern of decreasing tree density with higher elevations. In this region, increasing elevation is correlated with decreasing temperatures, increasing precipitation, and lower soil water holding capacity. This leads to two possible explanations for decreasing stem densities with elevation: temperature limitations or water limitations. To decouple these effects, we examined the effects of yearly potential relative radiation (PRR): low PRR sites ('north facing') showed a significantly higher tree density than high ('south facing') sites at the same elevation. The only explanation for the low and mid-elevation patterns is widespread water limitation, not light or temperature limitation. Increasing temperature with no further input of water, therefore, would only serve to further stress the trees and cause a lower densities and, therefore, a loss of forest habitat.

  7. The 4th Thermodynamic Principle?

    SciTech Connect

    Montero Garcia, Jose de la Luz; Novoa Blanco, Jesus Francisco

    2007-04-28

    It should be emphasized that the 4th Principle above formulated is a thermodynamic principle and, at the same time, is mechanical-quantum and relativist, as it should inevitably be and its absence has been one of main the theoretical limitations of the physical theory until today.We show that the theoretical discovery of Dimensional Primitive Octet of Matter, the 4th Thermodynamic Principle, the Quantum Hexet of Matter, the Global Hexagonal Subsystem of Fundamental Constants of Energy and the Measurement or Connected Global Scale or Universal Existential Interval of the Matter is that it is possible to be arrived at a global formulation of the four 'forces' or fundamental interactions of nature. The Einstein's golden dream is possible.

  8. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trade- offs

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Élodie; Hoffmann, Jordan; Carlotti, Alexis; Mawet, Dimitri

    2014-08-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and / or segment gaps. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a "missing segment" . Because the converging non-linear mappings resulting from our Deformable Mirror shapes damps near-field diffraction artifacts in the vicinity of the discontinuities this solution is particularly appealing in terms of spectral bandwidth. We present preliminary results that illustrate the performances of ACAD in the presence of diffraction for apertures for with secondary support structures of varying width and argue that the ultimate contrast achieved can by combining ACAD with modern wavefront control algorithms.

  9. Investigating the limits of PET/CT imaging at very low true count rates and high random fractions in ion-beam therapy monitoring

    SciTech Connect

    Kurz, Christopher Bauer, Julia; Conti, Maurizio; Guérin, Laura; Eriksson, Lars; Parodi, Katia

    2015-07-15

    reconstruction scheme has been applied to exemplary postirradiation patient data-sets. Results: Among the investigated reconstruction options, the overall best results in terms of image noise, activity quantification, and accurate geometrical recovery were achieved using the ordered subset expectation maximization reconstruction algorithm with time-of-flight (TOF) and point-spread function (PSF) information. For this algorithm, reasonably accurate (better than 5%) and precise (uncertainty of the mean activity below 10%) imaging can be provided down to 80 000 true coincidences at 96% RF. Image noise and geometrical fidelity are generally improved for fewer iterations. The main limitation for PET-based treatment monitoring has been identified in the small number of true coincidences, rather than the high intrinsic random background. Application of the optimized reconstruction scheme to patient data-sets results in a 25% − 50% reduced image noise at a comparable activity quantification accuracy and an improved geometrical performance with respect to the formerly used reconstruction scheme at HIT, adopted from nuclear medicine applications. Conclusions: Under the poor statistical conditions in PET-based treatment monitoring, improved results can be achieved by considering PSF and TOF information during image reconstruction and by applying less iterations than in conventional nuclear medicine imaging. Geometrical fidelity and image noise are mainly limited by the low number of true coincidences, not the high LSO-related random background. The retrieved results might also impact other emerging PET applications at low counting statistics.

  10. Combining Single RNA Sensitive Probes with Subdiffraction-Limited and Live-Cell Imaging Enables the Characterization of Virus Dynamics in Cells

    PubMed Central

    2013-01-01

    The creation of fluorescently labeled viruses is currently limited by the length of imaging observation time (e.g., labeling an envelope protein) and the rescue of viral infectivity (e.g., encoding a GFP protein). Using single molecule sensitive RNA hybridization probes delivered to the cytoplasm of infected cells, we were able to isolate individual, infectious, fluorescently labeled human respiratory syncytial virus virions. This was achieved without affecting viral mRNA expression, viral protein expression, or infectivity. Measurements included the characterization of viral proteins and genomic RNA in a single virion using dSTORM, the development of a GFP fusion assay, and the development of a pulse-chase assay for viral RNA production that allowed for the detection of both initial viral RNA and nascent RNA production at designated times postinfection. Live-cell measurements included imaging and characterization of filamentous virion fusion and the quantification of virus replication within the same cell over an eight-hour period. Using probe-labeled viruses, individual viral particles can be characterized at subdiffraction-limited resolution, and viral infections can be quantified in single cells over an entire cycle of replication. The implication of this development is that MTRIP labeling of viral RNA during virus assembly has the potential to become a general methodology for the labeling and study of many important RNA viruses. PMID:24351207

  11. Optimal Image Subtraction

    NASA Astrophysics Data System (ADS)

    Gal-Yam, Avishay; Zackay, Barak; Ofek, Eran O.

    2016-01-01

    Transient detection and flux measurement via image subtraction are fundamental to time domain astronomy. Starting from first principles, we develop the optimal linear statistic for transient detection and flux measurement and any other image-difference hypothesis testing. We derive a simple closed-form statistic that: (1) Is mathematically proven to be the optimal subtraction statistic in the limit of background-dominated noise within the family of linear solutions, that contains all previously suggested methods; (2) Does not leave subtraction or deconvolution artifacts, even in the vicinity of bright stars; (3) Is an order of magnitude faster to compute than popular methods; (4) Allowsautomatic transient detection down to the theoretical sensitivity limit by providing a reliable, well-defined detection significance; (5) Is symmetric to the interchange of the new and reference images; (6) Is numerically stable; and (7) Is trivial to implement. We demonstratethat the correct way to prepare a reference image is the proper image co-addition presented in Zackay & Ofek 2015. Finally, we show a proper image subtraction statistic, that, along with its point spread functions, is a sufficient statistic for any decision or measurement on the difference image. This allows accurate filtration of image artifacts such as cosmic rays and hot pixels. We demonstrate this method on simulated data as well as on observations from the Palomar Transient Factory.

  12. Chemical Principls Exemplified

    ERIC Educational Resources Information Center

    Plumb, Robert C.

    1973-01-01

    Two topics are discussed: (1) Stomach Upset Caused by Aspirin, illustrating principles of acid-base equilibrium and solubility; (2) Physical Chemistry of the Drinking Duck, illustrating principles of phase equilibria and thermodynamics. (DF)

  13. Principles of project management

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The basic principles of project management as practiced by NASA management personnel are presented. These principles are given as ground rules and guidelines to be used in the performance of research, development, construction or operational assignments.

  14. Deep Thermal Infrared Imaging of HR 8799 bcde: New Atmospheric Constraints and Limits on a Fifth Planet

    NASA Astrophysics Data System (ADS)

    Currie, Thayne; Burrows, Adam; Girard, Julien H.; Cloutier, Ryan; Fukagawa, Misato; Sorahana, Satoko; Kuchner, Marc; Kenyon, Scott J.; Madhusudhan, Nikku; Itoh, Yoichi; Jayawardhana, Ray; Matsumura, Soko; Pyo, Tae-Soo

    2014-11-01

    We present new L' (3.8 μm) and Brα (4.05 μm) data and reprocessed archival L' data for the young, planet-hosting star HR 8799 obtained with Keck/NIRC2, VLT/NaCo, and Subaru/IRCS. We detect all four HR 8799 planets in each data set at a moderate to high signal-to-noise ratio (S/N >~ 6-15). We fail to identify a fifth planet, "HR 8799 f," at r < 15 AU at a 5σ confidence level: one suggestive, marginally significant residual at 0.''2 is most likely a point-spread function artifact. Assuming companion ages of 30 Myr and the Baraffe planet cooling models, we rule out an HR 8799 f with a mass of 5 MJ (7 MJ ), 7 MJ (10 MJ ), or 12 MJ (13 MJ ) at r proj ~ 12 AU, 9 AU, and 5 AU, respectively. All four HR 8799 planets have red early T dwarf-like L' - [4.05] colors, suggesting that their spectral energy distributions peak in between the L' and M' broadband filters. We find no statistically significant difference in HR 8799 cde's color. Atmosphere models assuming thick, patchy clouds appear to better match HR 8799 bcde's photometry than models assuming a uniform cloud layer. While non-equilibrium carbon chemistry is required to explain HR 8799 b and c's photometry/spectra, evidence for it from HR 8799 d and e's photometry is weaker. Future, deep-IR spectroscopy/spectrophotometry with the Gemini Planet Imager, SCExAO/CHARIS, and other facilities may clarify whether the planets are chemically similar or heterogeneous.

  15. Deep thermal infrared imaging of HR 8799 bcde: new atmospheric constraints and limits on a fifth planet

    SciTech Connect

    Currie, Thayne; Cloutier, Ryan; Jayawardhana, Ray; Burrows, Adam; Girard, Julien H.; Fukagawa, Misato; Sorahana, Satoko; Kuchner, Marc; Kenyon, Scott J.; Madhusudhan, Nikku; Itoh, Yoichi; Matsumura, Soko; Pyo, Tae-Soo

    2014-11-10

    We present new L' (3.8 μm) and Brα (4.05 μm) data and reprocessed archival L' data for the young, planet-hosting star HR 8799 obtained with Keck/NIRC2, VLT/NaCo, and Subaru/IRCS. We detect all four HR 8799 planets in each data set at a moderate to high signal-to-noise ratio (S/N ≳ 6-15). We fail to identify a fifth planet, 'HR 8799 f', at r < 15 AU at a 5σ confidence level: one suggestive, marginally significant residual at 0.''2 is most likely a point-spread function artifact. Assuming companion ages of 30 Myr and the Baraffe planet cooling models, we rule out an HR 8799 f with a mass of 5 M{sub J} (7 M{sub J} ), 7 M{sub J} (10 M{sub J} ), or 12 M{sub J} (13 M{sub J} ) at r {sub proj} ∼ 12 AU, 9 AU, and 5 AU, respectively. All four HR 8799 planets have red early T dwarf-like L' – [4.05] colors, suggesting that their spectral energy distributions peak in between the L' and M' broadband filters. We find no statistically significant difference in HR 8799 cde's color. Atmosphere models assuming thick, patchy clouds appear to better match HR 8799 bcde's photometry than models assuming a uniform cloud layer. While non-equilibrium carbon chemistry is required to explain HR 8799 b and c's photometry/spectra, evidence for it from HR 8799 d and e's photometry is weaker. Future, deep-IR spectroscopy/spectrophotometry with the Gemini Planet Imager, SCExAO/CHARIS, and other facilities may clarify whether the planets are chemically similar or heterogeneous.

  16. Value and limitations of segmental analysis of stress thallium myocardial imaging for localization of coronary artery disease

    SciTech Connect

    Rigo, P.; Bailey, I.K.; Griffith, L.S.C.; Pitt, B.; Borow, R.D.; Wagner, H.N.; Becker, L.C.

    1980-05-01

    This study was done to determine the value of thallium-201 myocardial scintigraphic imaging (MSI) for identifying disease in the individual coronary arteries. Segmental analysis of rest and stress MSI was performed in 133 patients with ateriographically proved coronary artery disease (CAD). Certain scintigraphic segments were highly specific (97 to 100%) for the three major coronary arteries: anterior wall and septum for the left anterior descending (LAD) coronary artery; the inferior wall for the right coronary artery (RCA); and the proximal lateral wall for the circumflex (LCX) artery. Perfusion defects located in the anterolateral wall in the anterior view were highly specific for proximal disease in the LAD involving the major diagonal branches, but this was not true for septal defects. The apical segments were not specific for any of the three major vessels. Although MSI was abnormal in 89% of these patients with CAD, it was less sensitive for identifying individual vessel disease: 63% for LAD, 50% for RCA, and 21% for LCX disease (narrowings > = 50%). Sensitivity increased with the severity of stenosis, but even for 100% occlusions was only 87% for LAD, 58% for RCA and 38% for LCX. Sensitivity diminished as the number of vessels involved increased: with single-vessel disease, 80% of LAD, 54% of RAC and 33% of LCX lesions were detected, but in patients with triple-vessel disease, only 50% of LAD, 50% of RCA and 16% of LCX lesions were identified. Thus, although segmented analysis of MSI can identify disease in the individual coronary arteries with high specificity, only moderate sensitivity is achieved, reflecting the tendency of MSI to identify only the most severely ischemic area among several that may be present in a heart. Perfusion scintigrams display relative distributions rather than absolute values for myocardial blood flow.

  17. Principles of Modern Soccer.

    ERIC Educational Resources Information Center

    Beim, George

    This book is written to give a better understanding of the principles of modern soccer to coaches and players. In nine chapters the following elements of the game are covered: (1) the development of systems; (2) the principles of attack; (3) the principles of defense; (4) training games; (5) strategies employed in restarts; (6) physical fitness…

  18. Chemical Principles Exemplified

    ERIC Educational Resources Information Center

    Plumb, Robert C.

    1970-01-01

    This is the first of a new series of brief ancedotes about materials and phenomena which exemplify chemical principles. Examples include (1) the sea-lab experiment illustrating principles of the kinetic theory of gases, (2) snow-making machines illustrating principles of thermodynamics in gas expansions and phase changes, and (3) sunglasses that…

  19. The effect of receptor clustering on diffusion-limited forward rate constants.

    PubMed Central

    Goldstein, B; Wiegel, F W

    1983-01-01

    The effect of receptor clustering on the diffusion-limited forward rate constant (k+) is studied theoretically by modeling cell surface receptors by hemispheres distributed on a plane. We give both exact results and bounds. The exact results are obtained using an electrostatic analogue and applying the method of the images. Accurate upper bounds on k+ are found from a variational principle. PMID:6309261

  20. Image

    Energy Science and Technology Software Center (ESTSC)

    2007-08-31

    The computer side of the IMAGE project consists of a collection of Perl scripts that perform a variety of tasks; scripts are available to insert, update and delete data from the underlying Oracle database, download data from NCBI's Genbank and other sources, and generate data files for download by interested parties. Web scripts make up the tracking interface, and various tools available on the project web-site (image.llnl.gov) that provide a search interface to the database.

  1. Driving Toward Guiding Principles

    PubMed Central

    Buckovich, Suzy A.; Rippen, Helga E.; Rozen, Michael J.

    1999-01-01

    As health care moves from paper to electronic data collection, providing easier access and dissemination of health information, the development of guiding privacy, confidentiality, and security principles is necessary to help balance the protection of patients' privacy interests against appropriate information access. A comparative review and analysis was done, based on a compilation of privacy, confidentiality, and security principles from many sources. Principles derived from ten identified sources were compared with each of the compiled principles to assess support level, uniformity, and inconsistencies. Of 28 compiled principles, 23 were supported by at least 50 percent of the sources. Technology could address at least 12 of the principles. Notable consistencies among the principles could provide a basis for consensus for further legislative and organizational work. It is imperative that all participants in our health care system work actively toward a viable resolution of this information privacy debate. PMID:10094065

  2. Magnetism: Principles and Applications

    NASA Astrophysics Data System (ADS)

    Craik, Derek J.

    2003-09-01

    If you are studying physics, chemistry, materials science, electrical engineering, information technology or medicine, then you'll know that understanding magnetism is fundamental to success in your studies and here is the key to unlocking the mysteries of magnetism....... You can: obtain a simple overview of magnetism, including the roles of B and H, resonances and special techniques take full advantage of modern magnets with a wealth of expressions for fields and forces develop realistic general design programmes using isoparametric finite elements study the subtleties of the general theory of magnetic moments and their dynamics follow the development of outstanding materials appreciate how magnetism encompasses topics as diverse as rock magnetism, chemical reaction rates, biological compasses, medical therapies, superconductivity and levitation understand the basis and remarkable achievements of magnetic resonance imaging In his new book, Magnetism, Derek Craik throws light on the principles and applications of this fascinating subject. From formulae for calculating fields to quantum theory, the secrets of magnetism are exposed, ensuring that whether you are a chemist or engineer, physicist, medic or materials scientist Magnetism is the book for our course.

  3. Photoacoustic tomography: principles and advances

    PubMed Central

    Xia, Jun; Yao, Junjie; Wang, Lihong V.

    2014-01-01

    Photoacoustic tomography (PAT) is an emerging imaging modality that shows great potential for preclinical research and clinical practice. As a hybrid technique, PAT is based on the acoustic detection of optical absorption from either endogenous chromophores, such as oxy-hemoglobin and deoxy-hemoglobin, or exogenous contrast agents, such as organic dyes and nanoparticles. Because ultrasound scatters much less than light in tissue, PAT generates high-resolution images in both the optical ballistic and diffusive regimes. Over the past decade, the photoacoustic technique has been evolving rapidly, leading to a variety of exciting discoveries and applications. This review covers the basic principles of PAT and its different implementations. Strengths of PAT are highlighted, along with the most recent imaging results. PMID:25642127

  4. A new imaging technique for retinal vessel oximetry: principles and first clinical results in patients with retinal arterial occlusion and diabetic retinopathy

    NASA Astrophysics Data System (ADS)

    Hammer, M.; Riemer, T.; Vilser, W.; Gehlert, S.; Schweitzer, D.

    2009-02-01

    The oxygen saturation of blood inside retinal vessels is an essential measure for the estimation of oxygen supply to the tissue as well as its oxygen consumption. In the current approach, the blood oxygenation is measured by a dual-wavelength technique. Using a fundus camera, equipped with a special dual wavelength transmission filter and a color CCD camera, two monochromatic fundus images at 548 nm and 610 nm were recorded simultaneously. The optical densities of retinal vessels for both wavelengths and their ratio, which is known to be proportional to the oxygen saturation, were calculated. From a health control population, mean arterial and venous oxygen saturations were measured of 98+/-10.1% and 65+/-11.7% with reproducibility of 2.52% and 3.25% respectively. In 10 patients with arterial occlusion, a reduction of the arterial oxygen saturation to 78 +/-17% (mean +/- standard deviation, branch arterial occlusion) and 91+/-11% (central arterial occlusion) respectively was found in the occluded vessel. After 5 days on pentoxifilin therapy, the arterial saturation increased to an average of 93+/-12% or 103 +/-6% respectively. In 70 eyes of 42 patients suffering from diabetic retinopathy, an increase of the venous oxygen saturation with the severity of the retinopathy was found (mild nonproliferative retinopathy: 68.4+/-8.2%, moderate non-proliferative retinopathy: 70.5+/-6.8%, severe non-proliferative retinopathy: 72.4+/-7.6%, proliferative retinopathy 75.7+/-8.3%) due to vessel shunting and diabetic changes of the permeability of vessel walls. These first clinical results demonstrate the ability of an accurate measurement of retinal vessel oxygenation with a very simple setup just requiring a special filter in the illumination path of a fundus camera and dedicated software.

  5. The precautionary principle: is it safe.

    PubMed

    Gignon, Maxime; Ganry, Olivier; Jardé, Olivier; Manaouil, Cécile

    2013-06-01

    The precautionary principle is generally acknowledged to be a powerful tool for protecting health but it was originally invoked by policy makers for dealing with environmental issues. In the 1990s, the principle was incorporated into many legislative and regulatory texts in international law. One can consider that the precautionary principle has turned into "precautionism" necessary to prove to the people, taking account of risk in decisions. There is now a risk that these abuses will deprive the principle of its meaning and value. When pushed to its limits, the precautionary principle can even be dangerous when applied to the healthcare field. This is why a critical analysis of the principle is necessary. Through the literature, it sometimes seems to deviate somehow from the essence of the precautionary principle as it is commonly used in relation to health. We believe that educational work is necessary to familiarize professionals, policy makers and public opinion of the precautionary principle and avoid confusion. We propose a critical analysis of the use and misuse of the precautionary principle. PMID:23984492

  6. Principles of Bioremediation Assessment

    NASA Astrophysics Data System (ADS)

    Madsen, E. L.

    2001-12-01

    Although microorganisms have successfully and spontaneously maintained the biosphere since its inception, industrialized societies now produce undesirable chemical compounds at rates that outpace naturally occurring microbial detoxification processes. This presentation provides an overview of both the complexities of contaminated sites and methodological limitations in environmental microbiology that impede the documentation of biodegradation processes in the field. An essential step toward attaining reliable bioremediation technologies is the development of criteria which prove that microorganisms in contaminated field sites are truly active in metabolizing contaminants of interest. These criteria, which rely upon genetic, biochemical, physiological, and ecological principles and apply to both in situ and ex situ bioremediation strategies include: (i) internal conservative tracers; (ii) added conservative tracers; (iii) added radioactive tracers; (iv) added isotopic tracers; (v) stable isotopic fractionation patterns; (vi) detection of intermediary metabolites; (vii) replicated field plots; (viii) microbial metabolic adaptation; (ix) molecular biological indicators; (x) gradients of coreactants and/or products; (xi) in situ rates of respiration; (xii) mass balances of contaminants, coreactants, and products; and (xiii) computer modeling that incorporates transport and reactive stoichiometries of electron donors and acceptors. The ideal goal is achieving a quantitative understanding of the geochemistry, hydrogeology, and physiology of complex real-world systems.

  7. Images.

    ERIC Educational Resources Information Center

    Barr, Catherine, Ed.

    1997-01-01

    The theme of this month's issue is "Images"--from early paintings and statuary to computer-generated design. Resources on the theme include Web sites, CD-ROMs and software, videos, books, and others. A page of reproducible activities is also provided. Features include photojournalism, inspirational Web sites, art history, pop art, and myths. (AEF)

  8. Usage of medium-scale space images and GIS in analyzing the agriculture production limiting factors at the Northwestern coast, Egypt

    NASA Astrophysics Data System (ADS)

    Gad, A.

    2009-04-01

    The northwestern coast of Egypt is characterized by an international interest due to its history and magnificent environment. The area was known as being the bread basket during the Greek and Roman periods. Recently, drastic changes in land use resulting in destructing many of water harvesting tools, thus diminution of the agriculture importance. Restoration of the area and planning self sufficient communities needs to develop a sustainable land resources database for these regions. The medium scale space data provide a spatial resolution of 30 meters, in addition to multi-temporal imaging. Moreover, Geographic Information System (GIS) permits to store, merge, and manipulate the huge amounts of thematic maps and attribute data. A number of 7 Landsat ETM scenes covering the whole northwestern coast of Egypt were acquired and merged. ERDAS-IMAGINE software was used for image processing and analyzing. A number of 53 topographic maps at scale 1:50000 were used to input GIS thematic layers relevant to land resources, using Arc_GIS 9.2 system. Field investigation was carried out to represent different soil units and collect ground control points. Chemical and physical soil properties were determined, upon which soil classification was based. MicroLEIS system was employed to define soil restrictive elements for the local common agricultural practices. (i.e. cultivation of olives, peach, wheat, beans, and sunflower crops). The results showed that the presence of Calcic, Petrogypsic and Salic horizons are responsible for the problems of water logging, hard workability and secondary salinization. The identified great groups include Torripsamments, Torriorthents, Haplosalids, Petrogypsids and Haplocalcids. Soils of the alluvial fans and watershed basins are deep to moderately deep with a texture ranging between fine sand to clay loam. The salinity is relatively low (EC is +/- 2 dS/m) whereas the CaCO3 content is mostly over 8 %. The limiting factors found in the piedmont and

  9. Prediction of Flow-Limiting Fractional Flow Reserve in Patients With Stable Coronary Artery Disease Based on Quantitative Myocardial Perfusion Imaging.

    PubMed

    Tanaka, Haruki; Takahashi, Teruyuki; Kozono, Nami; Tanakamaru, Yoshiki; Ohashi, Norihiko; Yasunobu, Yuji; Tanaka, Koichi; Okada, Takenori; Kaseda, Shunichi; Nakanishi, Toshio; Kihara, Yasuki

    2016-05-01

    Although fractional flow reserve (FFR) and myocardial perfusion imaging (MPI) findings fundamentally differ, several cohort studies have revealed that these findings correlate. Here, we investigated whether flow-limiting FFR could be predicted from adenosine stress thallium-201 MPI with single-photon emission computed tomography (SPECT) findings derived from 84 consecutive, prospectively identified patients with stable coronary artery disease and 212 diseased vessels. Among them, FFR was measured in 136 diseased vessels (64%). The findings were compared with regional perfusion abnormalities including stress total perfusion defect (TPD) - rest TPD determined using quantitative perfusion single-photon emission computed tomography software. The FFR inversely correlated the most accurately with stress TPD - rest TPD (r = -0.552, p <0.001). Predictors of major vessels of interest comprising FFR <0.80, included stress TPD - rest TPD, the transient ischemic dilation ratio, left ventricular ejection fraction at rest and beta blockers for left anterior descending artery (LAD) regions, and stress TPD - rest TPD, left ventricular mass, left ventricular ejection fraction at rest, right coronary artery lesions, the transient ischemic dilation ratio, and age for non-LAD regions. The diagnostic accuracy of formulas to predict major vessels of interest with FFR <0.80 was high (sensitivity, specificity and accuracy for LAD and non-LAD: 84%, 87% and 86%, and 75%, 93% and 87%, respectively). In conclusion, although somewhat limited by a sample size and a single-center design, flow-limiting FFR could be predicted from MPI findings with a defined probability. A cohort study might validate our results and provide a novel adjunctive tool with which to diagnose functionally significant coronary artery disease from MPI findings. PMID:26970815

  10. Laser optoacoustic tomography for medical diagnostics: principles

    NASA Astrophysics Data System (ADS)

    Oraevsky, Alexander A.; Esenaliev, Rinat O.; Jacques, Steven L.; Tittel, Frank K.

    1996-04-01

    This paper is to describe principles of laser optoacoustic tomography for medical diagnostics. Two types of imaging modes are presented. The first is the tomography in transmission mode, which utilizes detection of stress transients transmitted from the laser-excited volume toward the depth through thick layers of tissue. The second is the tomography in reflection mode which utilizes detection of stress transients generated in superficial tissue layer and reflected back toward tissue surface. To distinguish the two modes, we have abbreviated them as (1) laser optoacoustic tomography in transmission mode, LOATT, and (2) time-resolved stress detection tomography of light absorption, TRSDTLA, in reflection mode where emphasis is made on high spatial resolution of images. The basis for laser optoacoustic tomography is the time-resolved detection of laser-induced transient stress waves, selectively generated in absorbing tissues of diagnostic interest. Such a technique allows one to visualize absorbed light distribution in turbid biological tissues irradiated by short laser pulses. Laser optoacoustic tomography can be used for detection of tissue pathological changes that result in either increased concentration of various tissue chromophores such as hemoglobin or in development of enhanced microcirculation in diseased tissue. Potential areas of applications are diagnosis of cancer, brain hemorrhages, arterial atherosclerotic plaques, and other diseased tissues. In addition, it can provide feedback information during medical treatments. Both LOATT and TRSDTLA utilize laser excitation of biological tissues and sensitive detection of laser-induced stress waves. Optical selectivity is based upon differences in optical properties of pathologically different tissues. Sensitivity comes from stress generation under irradiation conditions of temporal stress confinement. The use of sensitive wide-band lithium niobate acoustic transducers expands limits of laser optoacoustic

  11. The Real Limits to Growth

    ERIC Educational Resources Information Center

    Ross, W. A.

    1975-01-01

    Fundamental conservation principles indicate existence of a limit to growth operative in the near future. General properties of geometric growth are presented with timescales showing population increases. Projections for natural and energy resource consumption are examined. (BP)

  12. Artificial intelligence: Principles and applications

    SciTech Connect

    Yazdami, M.

    1985-01-01

    The book covers the principles of AI, the main areas of application, as well as considering some of the social implications. The applications chapters have a common format structured as follows: definition of the topic; approach with conventional computing techniques; why 'intelligence' would provide a better approach; and how AI techniques would be used and the limitations. The contents discussed are: Principles of artificial intelligence; AI programming environments; LISP, list processing and pattern-making; AI programming with POP-11; Computer processing of natural language; Speech synthesis and recognition; Computer vision; Artificial intelligence and robotics; The anatomy of expert systems - Forsyth; Machine learning; Memory models of man and machine; Artificial intelligence and cognitive psychology; Breaking out of the chinese room; Social implications of artificial intelligence; and Index.

  13. Time-encoded structured illumination microscopy: toward ultrafast superresolution imaging.

    PubMed

    Wang, Yuxi; Guo, Qiang; Chen, Hongwei; Chen, Minghua; Yang, Sigang; Xie, Shizhong

    2016-08-15

    An imaging strategy based on optical time-encoded structured illumination microscopy (TE-SIM) opens the way toward ultrafast superresolution imaging. A proof-of-principle experiment is conducted and the introduced TE-SIM accelerates the generation rate of sinusoidal fringe patterns to an unprecedented speed (dozens of megahertz). At such a high speed, superresolution imaging that surpasses the diffraction limit by a factor of 1.4 is demonstrated. This imaging strategy with high temporal and spatial resolution has great potential in many exciting applications, such as dynamic live cell imaging or high-throughput screening. PMID:27519081

  14. Guiding Principles for Evaluators.

    ERIC Educational Resources Information Center

    Shadish, William R., Ed.; And Others

    1995-01-01

    The 12 articles (including an index) of this theme issue are devoted to documenting and critiquing the American Evaluation Association's "Guiding Principles for Evaluators," a code of ethics and standards. The development of these principles is traced, and their strengths and weaknesses are analyzed at general and specific levels. (SLD)

  15. Assessment Principles and Tools

    PubMed Central

    Golnik, Karl C.

    2014-01-01

    The goal of ophthalmology residency training is to produce competent ophthalmologists. Competence can only be determined by appropriately assessing resident performance. There are accepted guiding principles that should be applied to competence assessment methods. These principles are enumerated herein and ophthalmology-specific assessment tools that are available are described. PMID:24791100

  16. Principled Grammar Teaching

    ERIC Educational Resources Information Center

    Batstone, Rob; Ellis, Rod

    2009-01-01

    A key aspect of the acquisition of grammar for second language learners involves learning how to make appropriate connections between grammatical forms and the meanings which they typically signal. We argue that learning form/function mappings involves three interrelated principles. The first is the Given-to-New Principle, where existing world…

  17. Hamilton's Principle for Beginners

    ERIC Educational Resources Information Center

    Brun, J. L.

    2007-01-01

    I find that students have difficulty with Hamilton's principle, at least the first time they come into contact with it, and therefore it is worth designing some examples to help students grasp its complex meaning. This paper supplies the simplest example to consolidate the learning of the quoted principle: that of a free particle moving along a…

  18. The genetic difference principle.

    PubMed

    Farrelly, Colin

    2004-01-01

    In the newly emerging debates about genetics and justice three distinct principles have begun to emerge concerning what the distributive aim of genetic interventions should be. These principles are: genetic equality, a genetic decent minimum, and the genetic difference principle. In this paper, I examine the rationale of each of these principles and argue that genetic equality and a genetic decent minimum are ill-equipped to tackle what I call the currency problem and the problem of weight. The genetic difference principle is the most promising of the three principles and I develop this principle so that it takes seriously the concerns of just health care and distributive justice in general. Given the strains on public funds for other important social programmes, the costs of pursuing genetic interventions and the nature of genetic interventions, I conclude that a more lax interpretation of the genetic difference principle is appropriate. This interpretation stipulates that genetic inequalities should be arranged so that they are to the greatest reasonable benefit of the least advantaged. Such a proposal is consistent with prioritarianism and provides some practical guidance for non-ideal societies--that is, societies that do not have the endless amount of resources needed to satisfy every requirement of justice. PMID:15186680

  19. The Principles of Leadership.

    ERIC Educational Resources Information Center

    Burns, Gerald P.

    The primary but not exclusive concern in this monograph is the principles and qualities of dynamic leaders of people rather than of ideas or cultural and artistic pursuits. Theories of leadership in the past, present, and future are discussed, as are the principles, rewards, exercise, and philosophy of leadership. A bibliography is included. (MSE)

  20. Government Information Policy Principles.

    ERIC Educational Resources Information Center

    Hernon, Peter

    1991-01-01

    Analyzes the utility of policy principles advanced by professional associations for public access to government information. The National Commission on Libraries and Information Science (NCLIS), the Information Industry Association (IIA), and the Office of Technology Assessment (OTA) urge the adoption of principles for the dissemination of public…

  1. Synchronized multiartifact reduction with tomographic reconstruction (SMART-RECON): A statistical model based iterative image reconstruction method to eliminate limited-view artifacts and to mitigate the temporal-average artifacts in time-resolved CT

    PubMed Central

    Chen, Guang-Hong; Li, Yinsheng

    2015-01-01

    Purpose: In x-ray computed tomography (CT), a violation of the Tuy data sufficiency condition leads to limited-view artifacts. In some applications, it is desirable to use data corresponding to a narrow temporal window to reconstruct images with reduced temporal-average artifacts. However, the need to reduce temporal-average artifacts in practice may result in a violation of the Tuy condition and thus undesirable limited-view artifacts. In this paper, the authors present a new iterative reconstruction method, synchronized multiartifact reduction with tomographic reconstruction (SMART-RECON), to eliminate limited-view artifacts using data acquired within an ultranarrow temporal window that severely violates the Tuy condition. Methods: In time-resolved contrast enhanced CT acquisitions, image contrast dynamically changes during data acquisition. Each image reconstructed from data acquired in a given temporal window represents one time frame and can be denoted as an image vector. Conventionally, each individual time frame is reconstructed independently. In this paper, all image frames are grouped into a spatial–temporal image matrix and are reconstructed together. Rather than the spatial and/or temporal smoothing regularizers commonly used in iterative image reconstruction, the nuclear norm of the spatial–temporal image matrix is used in SMART-RECON to regularize the reconstruction of all image time frames. This regularizer exploits the low-dimensional structure of the spatial–temporal image matrix to mitigate limited-view artifacts when an ultranarrow temporal window is desired in some applications to reduce temporal-average artifacts. Both numerical simulations in two dimensional image slices with known ground truth and in vivo human subject data acquired in a contrast enhanced cone beam CT exam have been used to validate the proposed SMART-RECON algorithm and to demonstrate the initial performance of the algorithm. Reconstruction errors and temporal fidelity

  2. Principlism and communitarianism.

    PubMed

    Callahan, D

    2003-10-01

    The decline in the interest in ethical theory is first outlined, as a background to the author's discussion of principlism. The author's own stance, that of a communitarian philosopher, is then described, before the subject of principlism itself is addressed. Two problems stand in the way of the author's embracing principlism: its individualistic bias and its capacity to block substantive ethical inquiry. The more serious problem the author finds to be its blocking function. Discussing the four scenarios the author finds that the utility of principlism is shown in the two scenarios about Jehovah's Witnesses but that when it comes to selling kidneys for transplantation and germline enhancement, principlism is of little help. PMID:14519838

  3. The close circumstellar environment of Betelgeuse. II. Diffraction-limited spectro-imaging from 7.76 to 19.50 μm with VLT/VISIR

    NASA Astrophysics Data System (ADS)

    Kervella, P.; Perrin, G.; Chiavassa, A.; Ridgway, S. T.; Cami, J.; Haubois, X.; Verhoelst, T.

    2011-07-01

    Context. Mass-loss occurring in red supergiants (RSGs) is a major contributor to the enrichment of the interstellar medium in dust and molecules. The physical mechanism of this mass loss is however relatively poorly known. Betelgeuse is the nearest RSG, and as such a prime object for high angular resolution observations of its surface (by interferometry) and close circumstellar environment. Aims: The goal of our program is to understand how the material expelled from Betelgeuse is transported from its surface to the interstellar medium, and how it evolves chemically in this process. Methods: We obtained diffraction-limited images of Betelgeuse and a calibrator (Aldebaran) in six filters in the N band (7.76 to 12.81 μm) and two filters in the Q band (17.65 and 19.50 μm), using the VLT/VISIR instrument. Results: Our images show a bright, extended and complex circumstellar envelope at all wavelengths. It is particularly prominent longwards of ≈ 9-10 μm, pointing at the presence of O-rich dust, such as silicates or alumina. A partial circular shell is observed between 0.5 and 1.0″ from the star, and could correspond to the inner radius of the dust envelope. Several knots and filamentary structures are identified in the nebula. One of the knots, located at a distance of 0.9″ west of the star, is particularly bright and compact. Conclusions: The circumstellar envelope around Betelgeuse extends at least up to several tens of stellar radii. Its relatively high degree of clumpiness indicates an inhomogeneous spatial distribution of the material lost by the star. Its extension corresponds to an important intermediate scale, where most of the dust is probably formed, between the hot and compact gaseous envelope observed previously in the near infrared and the interstellar medium. Based on observations made with ESO telescopes at Paranal Observatory, under ESO DDT program 286.D-5007(A).

  4. Gamma-ray Imaging Methods

    SciTech Connect

    Vetter, K; Mihailescu, L; Nelson, K; Valentine, J; Wright, D

    2006-10-05

    In this document we discuss specific implementations for gamma-ray imaging instruments including the principle of operation and describe systems which have been built and demonstrated as well as systems currently under development. There are several fundamentally different technologies each with specific operational requirements and performance trade offs. We provide an overview of the different gamma-ray imaging techniques and briefly discuss challenges and limitations associated with each modality (in the appendix we give detailed descriptions of specific implementations for many of these technologies). In Section 3 we summarize the performance and operational aspects in tabular form as an aid for comparing technologies and mapping technologies to potential applications.

  5. Imaging Genetics

    ERIC Educational Resources Information Center

    Munoz, Karen E.; Hyde, Luke W.; Hariri, Ahmad R.

    2009-01-01

    Imaging genetics is an experimental strategy that integrates molecular genetics and neuroimaging technology to examine biological mechanisms that mediate differences in behavior and the risks for psychiatric disorder. The basic principles in imaging genetics and the development of the field are discussed.

  6. Progress in 3D imaging and display by integral imaging

    NASA Astrophysics Data System (ADS)

    Martinez-Cuenca, R.; Saavedra, G.; Martinez-Corral, M.; Pons, A.; Javidi, B.

    2009-05-01

    Three-dimensionality is currently considered an important added value in imaging devices, and therefore the search for an optimum 3D imaging and display technique is a hot topic that is attracting important research efforts. As main value, 3D monitors should provide the observers with different perspectives of a 3D scene by simply varying the head position. Three-dimensional imaging techniques have the potential to establish a future mass-market in the fields of entertainment and communications. Integral imaging (InI), which can capture true 3D color images, has been seen as the right technology to 3D viewing to audiences of more than one person. Due to the advanced degree of development, InI technology could be ready for commercialization in the coming years. This development is the result of a strong research effort performed along the past few years by many groups. Since Integral Imaging is still an emerging technology, the first aim of the "3D Imaging and Display Laboratory" at the University of Valencia, has been the realization of a thorough study of the principles that govern its operation. Is remarkable that some of these principles have been recognized and characterized by our group. Other contributions of our research have been addressed to overcome some of the classical limitations of InI systems, like the limited depth of field (in pickup and in display), the poor axial and lateral resolution, the pseudoscopic-to-orthoscopic conversion, the production of 3D images with continuous relief, or the limited range of viewing angles of InI monitors.

  7. Development and Validation of Non-Integrative, Self-Limited, and Replicating Minicircles for Safe Reporter Gene Imaging of Cell-Based Therapies

    PubMed Central

    Ronald, John A.; Cusso, Lorena; Chuang, Hui-Yen; Yan, Xinrui; Dragulescu-Andrasi, Anca; Gambhir, Sanjiv Sam

    2013-01-01

    Reporter gene (RG) imaging of cell-based therapies provides a direct readout of therapeutic efficacy by assessing the fate of implanted cells. To permit long-term cellular imaging, RGs are traditionally required to be integrated into the cellular genome. This poses a potential safety risk and regulatory bottleneck for clinical translation as integration can lead to cellular transformation. To address this issue, we have developed non-integrative, replicating minicircles (MCs) as an alternative platform for safer monitoring of cells in living subjects. We developed both plasmids and minicircles containing the scaffold/matrix attachment regions (S/MAR) of the human interferon-beta gene, driven by the CMV promoter, and expressing the bioluminescence RG firefly luciferase. Constructs were transfected into breast cancer cells, and expanded S/MAR minicircle clones showed luciferase signal for greater than 3 months in culture and minicircles remained as episomes. Importantly, luciferase activity in clonal populations was slowly lost over time and this corresponded to a loss of episome, providing a way to reversibly label cells. To monitor cell proliferation in vivo, 1.5×106 cells carrying the S/MAR minicircle were implanted subcutaneously into mice (n = 5) and as tumors developed significantly more bioluminescence signal was noted at day 35 and 43 compared to day 7 post-implant (p<0.05). To our knowledge, this is the first work examining the use of episomal, self-limited, replicating minicircles to track the proliferation of cells using non-invasive imaging in living subjects. Continued development of S/MAR minicircles will provide a broadly applicable vector platform amenable with any of the numerous RG technologies available to allow therapeutic cell fate to be assessed in individual patients, and to achieve this without the need to manipulate the cell's genome so that safety concerns are minimized. This will lead to safe tools to assess treatment response at

  8. DIRECT IMAGING AND SPECTROSCOPY OF A CANDIDATE COMPANION BELOW/NEAR THE DEUTERIUM-BURNING LIMIT IN THE YOUNG BINARY STAR SYSTEM, ROXs 42B

    SciTech Connect

    Currie, Thayne; Daemgen, Sebastian; Jayawardhana, Ray; Debes, John; Lafreniere, David; Itoh, Yoichi; Ratzka, Thorsten; Correia, Serge

    2014-01-10

    We present near-infrared high-contrast imaging photometry and integral field spectroscopy of ROXs 42B, a binary M0 member of the 1-3 Myr old ρ Ophiuchus star-forming region, from data collected over 7 years. Each data set reveals a faint companion—ROXs 42Bb—located ∼1.''16 (r {sub proj} ≈ 150 AU) from the primaries at a position angle consistent with a point source identified earlier by Ratzka et al.. ROXs 42Bb's astrometry is inconsistent with a background star but consistent with a bound companion, possibly one with detected orbital motion. The most recent data set reveals a second candidate companion at ∼0.''5 of roughly equal brightness, though preliminary analysis indicates it is a background object. ROXs 42Bb's H and K{sub s} band photometry is similar to dusty/cloudy young, low-mass late M/early L dwarfs. K band VLT/SINFONI spectroscopy shows ROXs 42Bb to be a cool substellar object (M8-L0; T {sub eff} ≈ 1800-2600 K), not a background dwarf star, with a spectral shape indicative of young, low surface gravity planet-mass companions. We estimate ROXs 42Bb's mass to be 6-15 M{sub J} , either below the deuterium-burning limit and thus planet mass or straddling the deuterium-burning limit nominally separating planet-mass companions from other substellar objects. Given ROXs 42b's projected separation and mass with respect to the primaries, it may represent the lowest mass objects formed like binary stars or a class of planet-mass objects formed by protostellar disk fragmentation/disk instability, the latter slightly blurring the distinction between non-deuterium-burning planets like HR 8799 bcde and low-mass, deuterium-burning brown dwarfs.

  9. Maxillofacial Fractures: Midface and Internal Orbit-Part II: Principles and Surgical Treatment.

    PubMed

    Mast, Gerson; Ehrenfeld, Michael; Cornelius, Carl-Peter; Tasman, Abel-Jan; Litschel, Ralph

    2015-08-01

    Current clinical assessment and imaging techniques were described in part 1, and this article presents a systematic review of the surgical treatment principles in the management of midface and internal orbit fractures from initial care to definitive treatment, including illustrative case examples. New developments enabled limited surgical approaches by standardization of osteosynthesis principles regarding three-dimensional buttress reconstruction, by newly developed individualized implants such as titanium meshes and, especially for complex fracture patterns, by critical assessment of anatomical reconstruction through intraoperative endoscopy, as well as intra- and postoperative imaging. Resorbable soft tissue anchors can be used both for ligament and soft tissue resuspension to reduce ptosis effects in the cheeks and nasolabial area and to achieve facial aesthetics similar to those prior to the injury. PMID:26372710

  10. Principles of ecosystem sustainability

    SciTech Connect

    Chapin, F.S. III; Torn, M.S.; Tateno, Masaki

    1996-12-01

    Many natural ecosystems are self-sustaining, maintaining an characteristic mosaic of vegetation types of hundreds to thousands of years. In this article we present a new framework for defining the conditions that sustain natural ecosystems and apply these principles to sustainability of managed ecosystems. A sustainable ecosystem is one that, over the normal cycle of disturbance events, maintains its characteristics diversity of major functional groups, productivity, and rates of biogeochemical cycling. These traits are determined by a set of four {open_quotes}interactive controls{close_quotes} (climate, soil resource supply, major functional groups of organisms, and disturbance regime) that both govern and respond to ecosystem processes. Ecosystems cannot be sustained unless the interactive controls oscillate within stable bounds. This occurs when negative feedbacks constrain changes in these controls. For example, negative feedbacks associated with food availability and predation often constrain changes in the population size of a species. Linkages among ecosystems in a landscape can contribute to sustainability by creating or extending the feedback network beyond a single patch. The sustainability of managed systems can be increased by maintaining interactive controls so that they form negative feedbacks within ecosystems and by using laws and regulations to create negative feedbacks between ecosystems and human activities, such as between ocean ecosystems and marine fisheries. Degraded ecosystems can be restored through practices that enhance positive feedbacks to bring the ecosystem to a state where the interactive controls are commensurate with desired ecosystem characteristics. The possible combinations of interactive controls that govern ecosystem traits are limited by the environment, constraining the extent to which ecosystems can be managed sustainably for human purposes. 111 refs., 3 figs., 2 tabs.

  11. Nanodosimetry: Principle and Current Status

    NASA Astrophysics Data System (ADS)

    Schulte, Reinhard W.

    2011-05-01

    Due to the success of theoretical track structure Monte Carlo simulations, showing that features of ionization patterns on the nanometer level are important for the biological effectiveness of ionizing radiation, several new methods for experimental track structure investigations have been developed in recent years. These methods all use the principle of density scaling in low-pressure gas to probe track structure in macroscopic dimensions, ideally with single-ionization resolution. The new field of experimental track structure investigation, which has been called nanodosimetry, can be approached in two ways: (1) the number of ionizations in a defined, ideally wall-less, sensitive volume is registered per single primary particle and cluster size distributions are obtained, or (2) the full track structure of an ion track segment is "imaged". Existing nanodosimetric methods are based on the first approach, but a track structure imaging detector is currently under development at Loma Linda University. This contribution will review the principle and existing technical approaches to nanodosimetry and will give an outlook on future developments and applications.

  12. Nanodosimetry: Principle and Current Status

    SciTech Connect

    Schulte, Reinhard W.

    2011-05-05

    Due to the success of theoretical track structure Monte Carlo simulations, showing that features of ionization patterns on the nanometer level are important for the biological effectiveness of ionizing radiation, several new methods for experimental track structure investigations have been developed in recent years. These methods all use the principle of density scaling in low-pressure gas to probe track structure in macroscopic dimensions, ideally with single-ionization resolution. The new field of experimental track structure investigation, which has been called nanodosimetry, can be approached in two ways: (1) the number of ionizations in a defined, ideally wall-less, sensitive volume is registered per single primary particle and cluster size distributions are obtained, or (2) the full track structure of an ion track segment is 'imaged'. Existing nanodosimetric methods are based on the first approach, but a track structure imaging detector is currently under development at Loma Linda University. This contribution will review the principle and existing technical approaches to nanodosimetry and will give an outlook on future developments and applications.

  13. Archimedes' Principle in Action

    ERIC Educational Resources Information Center

    Kires, Marian

    2007-01-01

    The conceptual understanding of Archimedes' principle can be verified in experimental procedures which determine mass and density using a floating object. This is demonstrated by simple experiments using graduated beakers. (Contains 5 figures.)

  14. Chemical Principles Exemplified

    ERIC Educational Resources Information Center

    Plumb, Robert C.

    1972-01-01

    Collection of two short descriptions of chemical principles seen in life situations: the autocatalytic reaction seen in the bombardier beetle, and molecular potential energy used for quick roasting of beef. Brief reference is also made to methanol lighters. (PS)

  15. Global ethics and principlism.

    PubMed

    Gordon, John-Stewart

    2011-09-01

    This article examines the special relation between common morality and particular moralities in the four-principles approach and its use for global ethics. It is argued that the special dialectical relation between common morality and particular moralities is the key to bridging the gap between ethical universalism and relativism. The four-principles approach is a good model for a global bioethics by virtue of its ability to mediate successfully between universal demands and cultural diversity. The principle of autonomy (i.e., the idea of individual informed consent), however, does need to be revised so as to make it compatible with alternatives such as family- or community-informed consent. The upshot is that the contribution of the four-principles approach to global ethics lies in the so-called dialectical process and its power to deal with cross-cultural issues against the background of universal demands by joining them together. PMID:22073817

  16. Principles of Tendon Transfer.

    PubMed

    Wilbur, Danielle; Hammert, Warren C

    2016-08-01

    Tendon transfers provide a substitute, either temporary or permanent, when function is lost due to neurologic injury in stroke, cerebral palsy or central nervous system lesions, peripheral nerve injuries, or injuries to the musculotendinous unit itself. This article reviews the basic principles of tendon transfer, which are important when planning surgery and essential for an optimal outcome. In addition, concepts for coapting the tendons during surgery and general principles to be followed during the rehabilitation process are discussed. PMID:27387072

  17. Toward full-chip prediction of yield-limiting contact patterning failure: correlation of simulated image parameters to advanced contact metrology metrics

    NASA Astrophysics Data System (ADS)

    Sturtevant, John L.; Chou, Dyiann

    2006-03-01

    Electrical failure due to incomplete contacts or vias has arisen as one of the primary modes of yield loss for 130 nm and below designs in manufacturing. Such failures are generally understood to arise from both random and systematic sources. The addition of redundant vias, where possible, has long been an accepted DFM practice for mitigating the impact of random defects. Incomplete vias are often characterized by having a diameter near the target dimension but a depth of less than 100% of target. As such, it is a difficult problem to diagnose and debug in-line, since bright and dark field optical inspection systems cannot typically distinguish between a closed, partially open and fully open contact. Advanced metrology systems have emerged in recent years to meet this challenge, but no perfect manufacturing solution has yet been identified for full field verification of all contacts. Voltage Contrast (VC) SEM metrology biases the wafer to directly measure electrical conductivity after fill / polish, and can therefore easily discern a lack of electrical connection to the underlying conductor caused by incomplete photo, etch, or fill processing. While an entire wafer can in principal be VC scanned, throughput limitations dictate very sparse sampling in manufacturing. SEM profile grading (PG) leverages the rich content of the secondary electron waveform to decipher information about the bottom of the contact. Several authors have demonstrated an excellent response of the Profile Grade to intentional defocus vectors. However, the SEM can only target discreet or single digit groupings of contacts, and therefore requires intelligent guidance to identify those contacts which are most prone to failure, enabling protection of the fab WIP. An a-priori knowledge of which specific contacts in a layout are most likely to fail would prove very useful for proactive inspection in manufacturing. Model based pre-manufacturing verification allows for such knowledge to be communicated

  18. Diffraction enhance x-ray imaging for quantitative phase contrast studies

    NASA Astrophysics Data System (ADS)

    Agrawal, A. K.; Singh, B.; Kashyap, Y. S.; Shukla, Mayank; Sarkar, P. S.; Sinha, Amar

    2016-05-01

    Conventional X-ray imaging based on absorption contrast permits limited visibility of feature having small density and thickness variations. For imaging of weakly absorbing material or materials possessing similar densities, a novel phase contrast imaging techniques called diffraction enhanced imaging has been designed and developed at imaging beamline Indus-2 RRCAT Indore. The technique provides improved visibility of the interfaces and show high contrast in the image forsmall density or thickness gradients in the bulk. This paper presents basic principle, instrumentation and analysis methods for this technique. Initial results of quantitative phase retrieval carried out on various samples have also been presented.

  19. Testing the Pauli Exclusion Principle for Electrons

    NASA Astrophysics Data System (ADS)

    Marton, J.; Bartalucci, S.; Bertolucci, S.; Berucci, C.; Bragadireanu, M.; Cargnelli, M.; Curceanu (Petrascu, C.; Di Matteo, S.; Egger, J.-P.; Guaraldo, C.; Iliescu, M.; Ishiwatari, T.; Laubenstein, M.; Milotti, E.; Pietreanu, D.; Piscicchia, K.; Ponta, T.; Romero Vidal, A.; Scordo, A.; Sirghi, D. L.; Sirghi, F.; Sperandio, L.; Vazquez Doce, O.; Widmann, E.; Zmeskal, J.

    2013-07-01

    One of the fundamental rules of nature and a pillar in the foundation of quantum theory and thus of modern physics is represented by the Pauli Exclusion Principle. We know that this principle is extremely well fulfilled due to many observations. Numerous experiments were performed to search for tiny violation of this rule in various systems. The experiment VIP at the Gran Sasso underground laboratory is searching for possible small violations of the Pauli Exclusion Principle for electrons leading to forbidden X-ray transitions in copper atoms. VIP is aiming at a test of the Pauli Exclusion Principle for electrons with high accuracy, down to the level of 10-29 - 10-30, thus improving the previous limit by 3-4 orders of magnitude. The experimental method, results obtained so far and new developments within VIP2 (follow-up experiment at Gran Sasso, in preparation) to further increase the precision by 2 orders of magnitude will be presented.

  20. Evidence of Limited Motion of the Prostate by Carefully Emptying the Rectum as Assessed by Daily MVCT Image Guidance with Helical Tomotherapy

    SciTech Connect

    Fiorino, Claudio Ph.D. Di Muzio, Nadia; Broggi, Sara; Cozzarini, Cesare; Maggiulli, Eleonora M.Sc.; Alongi, Filippo; Valdagni, Riccardo; Fazio, Ferruccio; Calandrino, Riccardo

    2008-06-01

    Purpose: To assess setup and organ motion error by means of analysis of daily megavoltage computed tomography (MVCT) of patients treated with hypofractionated helical tomotherapy (71.4-74.2 Gy in 28 fractions). Methods and Materials: Data from 21 patients were analyzed. Patients were instructed to empty the rectum carefully before planning CT and every morning before therapy by means of a self-applied rectal enema. The position of the prostate was assessed by means of automatic bone matching (BM) with the planning kilovoltage CT (BM, setup error) followed by a direct visualization (DV) match on the prostate. Deviations between planning and therapy positions referred to BM and BM + DV were registered for the three main axes. In case of a full rectum at MVCT with evident shift of the prostate, treatment was postponed until after additional rectal emptying procedures; in this case, additional MVCT was performed before delivering the treatment. Data for 522 fractions were available; the impact of post-MVCT procedure was investigated for 17 of 21 patients (410 fractions). Results: Prostate motion relative to bony anatomy was limited. Concerning posterior-anterior shifts, only 4.9% and 2.7% of fractions showed deviation of 3 mm or greater of the prostate relative to BM without and with consideration of post-MVCT procedures, respectively. Interobserver variability for BM + DV match was within 0.8 mm (1 SD). Conclusions: Daily MVCT-based correction is feasible. The BM + DV matching was found to be consistent between operators. Rectal emptying using a daily enema is an efficient tool to minimize prostate motion, even for centers that have not yet implemented image-guided radiotherapy.

  1. Optimality principles for the visual code

    NASA Astrophysics Data System (ADS)

    Pitkow, Xaq

    One way to try to make sense of the complexities of our visual system is to hypothesize that evolution has developed nearly optimal solutions to the problems organisms face in the environment. In this thesis, we study two such principles of optimality for the visual code. In the first half of this dissertation, we consider the principle of decorrelation. Influential theories assert that the center-surround receptive fields of retinal neurons remove spatial correlations present in the visual world. It has been proposed that this decorrelation serves to maximize information transmission to the brain by avoiding transfer of redundant information through optic nerve fibers of limited capacity. While these theories successfully account for several aspects of visual perception, the notion that the outputs of the retina are less correlated than its inputs has never been directly tested at the site of the putative information bottleneck, the optic nerve. We presented visual stimuli with naturalistic image correlations to the salamander retina while recording responses of many retinal ganglion cells using a microelectrode array. The output signals of ganglion cells are indeed decorrelated compared to the visual input, but the receptive fields are only partly responsible. Much of the decorrelation is due to the nonlinear processing by neurons rather than the linear receptive fields. This form of decorrelation dramatically limits information transmission. Instead of improving coding efficiency we show that the nonlinearity is well suited to enable a combinatorial code or to signal robust stimulus features. In the second half of this dissertation, we develop an ideal observer model for the task of discriminating between two small stimuli which move along an unknown retinal trajectory induced by fixational eye movements. The ideal observer is provided with the responses of a model retina and guesses the stimulus identity based on the maximum likelihood rule, which involves sums

  2. An Inconvenient Principle

    NASA Astrophysics Data System (ADS)

    Bellac, Michel Le

    2014-11-01

    At the end of the XIXth century, physics was dominated by two main theories: classical (or Newtonian) mechanics and electromagnetism. To be entirely correct, we should add thermodynamics, which seemed to be grounded on different principles, but whose links with mechanics were progressively better understood thanks to the work of Maxwell and Boltzmann, among others. Classical mechanics, born with Galileo and Newton, claimed to explain the motion of lumps of matter under the action of forces. The paradigm for a lump of matter is a particle, or a corpuscle, which one can intuitively think of as a billiard ball of tiny dimensions, and which will be dubbed a micro-billiard ball in what follows. The second main component of XIXth century physics, electromagnetism, is a theory of the electric and magnetic fields and also of optics, thanks to the synthesis between electromagnetism and optics performed by Maxwell, who understood that light waves are nothing other than a particular case of electromagnetic waves. We had, on the one hand, a mechanical theory where matter exhibiting a discrete character (particles) was carried along well localized trajectories and, on the other hand, a wave theory describing continuous phenomena which did not involve transport of matter. The two theories addressed different domains, the only obvious link being the law giving the force on a charged particle submitted to an electromagnetic field, or Lorentz force. In 1905, Einstein put an end to this dichotomic wave/particle view and launched two revolutions of physics: special relativity and quantum physics. First, he showed that Newton's equations of motion must be modified when the particle velocities are not negligible with respect to that of light: this is the special relativity revolution, which introduces in mechanics a quantity characteristic of optics, the velocity of light. However, this is an aspect of the Einsteinian revolution which will not interest us directly, with the exception

  3. A quantitative, non-interferometric X-ray phase contrast imaging technique

    PubMed Central

    Munro, Peter R.T.; Rigon, Luigi; Ignatyev, Konstantin; Lopez, Frances C.M.; Dreossi, Diego; Speller, Robert D.; Olivo, Alessandro

    2013-01-01

    We present a quantitative, non-interferometric, X-ray differential phase contrast imaging technique based on the edge illumination principle. We derive a novel phase retrieval algorithm which requires only two images to be acquired and verify the technique experimentally using synchrotron radiation. The technique is useful for planar imaging but is expected to be important for quantitative phase tomography also. The properties and limitations of the technique are studied in detail. PMID:23388958

  4. Applying the four principles.

    PubMed

    Macklin, R

    2003-10-01

    Gillon is correct that the four principles provide a sound and useful way of analysing moral dilemmas. As he observes, the approach using these principles does not provide a unique solution to dilemmas. This can be illustrated by alternatives to Gillon's own analysis of the four case scenarios. In the first scenario, a different set of factual assumptions could yield a different conclusion about what is required by the principle of beneficence. In the second scenario, although Gillon's conclusion is correct, what is open to question is his claim that what society regards as the child's best interest determines what really is in the child's best interest. The third scenario shows how it may be reasonable for the principle of beneficence to take precedence over autonomy in certain circumstances, yet like the first scenario, the ethical conclusion relies on a set of empirical assumptions and predictions of what is likely to occur. The fourth scenario illustrates how one can draw different conclusions based on the importance given to the precautionary principle. PMID:14519836

  5. Connection of Scattering Principles: A Visual and Mathematical Tour

    ERIC Educational Resources Information Center

    Broggini, Filippo; Snieder, Roel

    2012-01-01

    Inverse scattering, Green's function reconstruction, focusing, imaging and the optical theorem are subjects usually studied as separate problems in different research areas. We show a physical connection between the principles because the equations that rule these "scattering principles" have a similar functional form. We first lead the reader…

  6. Quantum limits of thermometry

    SciTech Connect

    Stace, Thomas M.

    2010-07-15

    The precision of typical thermometers consisting of N particles scales as {approx}1/{radical}(N). For high-precision thermometry and thermometric standards, this presents an important theoretical noise floor. Here it is demonstrated that thermometry may be mapped onto the problem of phase estimation, and using techniques from optimal phase estimation, it follows that the scaling of the precision of a thermometer may in principle be improved to {approx}1/N, representing a Heisenberg limit to thermometry.

  7. Spaceborne receivers: Basic principles

    NASA Technical Reports Server (NTRS)

    Stacey, J. M.

    1984-01-01

    The underlying principles of operation of microwave receivers for space observations of planetary surfaces were examined. The design philosophy of the receiver as it is applied to operate functionally as an efficient receiving system, the principle of operation of the key components of the receiver, and the important differences among receiver types are explained. The operating performance and the sensitivity expectations for both the modulated and total power receiver configurations are outlined. The expressions are derived from first principles and are developed through the important intermediate stages to form practicle and easily applied equations. The transfer of thermodynamic energy from point to point within the receiver is illustrated. The language of microwave receivers is applied statistics.

  8. Basics, principles, techniques and modern methods in paediatric ultrasonography.

    PubMed

    Riccabona, Michael

    2014-09-01

    Ultrasonography (US) is the mainstay of paediatric Radiology. This review aims at revisiting basic US principles, to list specific needs throughout childhood, and to discuss the application of new and modern US methods. The various sections elude to basic US physics, technical requisites and tips for handling, diagnostically valuable applications of modern techniques, and how to properly address hazards, risks and limitations. In conclusion, US holds vast potential throughout childhood in almost all body regions and many childhood specific queries - helping to reduce the need for or to optimize more invasive or irradiating imaging. Make the most of US and offerings a dedicated paediatric US service throughout the day, the week and the year thus is and will stay a major task of Paediatric Radiology. PMID:24932845

  9. Teaching/learning principles

    NASA Technical Reports Server (NTRS)

    Hankins, D. B.; Wake, W. H.

    1981-01-01

    The potential remote sensing user community is enormous, and the teaching and training tasks are even larger; however, some underlying principles may be synthesized and applied at all levels from elementary school children to sophisticated and knowledgeable adults. The basic rules applying to each of the six major elements of any training course and the underlying principle involved in each rule are summarized. The six identified major elements are: (1) field sites for problems and practice; (2) lectures and inside study; (3) learning materials and resources (the kit); (4) the field experience; (5) laboratory sessions; and (6) testing and evaluation.

  10. Itch Management: General Principles.

    PubMed

    Misery, Laurent

    2016-01-01

    Like pain, itch is a challenging condition that needs to be managed. Within this setting, the first principle of itch management is to get an appropriate diagnosis to perform an etiology-oriented therapy. In several cases it is not possible to treat the cause, the etiology is undetermined, there are several causes, or the etiological treatment is not effective enough to alleviate itch completely. This is also why there is need for symptomatic treatment. In all patients, psychological support and associated pragmatic measures might be helpful. General principles and guidelines are required, yet patient-centered individual care remains fundamental. PMID:27578069

  11. The performance of photon counting imaging with a Geiger mode silicon avalanche photodiode

    NASA Astrophysics Data System (ADS)

    Qu, Hui-Ming; Zhang, Yi-Fan; Ji, Zhong-Jie; Chen, Qian

    2013-10-01

    In principle, photon counting imaging can detect a photon. With the development of low-level-light image intensifier techniques and low-level-light detection devices, photon counting imaging can now detect photon images under extremely low illumination. Based on a Geiger mode silicon avalanche photodiode single photon counter, an experimental system for photon counting imaging was built through two-dimensional scanning of a SPAD (single photon avalanche diode) detector. The feasibility of the imaging platform was validated experimentally. Two images with different characteristics, namely, the USAF 1951 resolution test panel and the image of Lena, were chosen to evaluate the imaging performance of the experimental system. The results were compared and analysed. The imaging properties under various illumination and scanning steps were studied. The lowest illumination limit of the SPAD photon counting imaging was determined.

  12. Ultrasound elastography: principles, techniques, and clinical applications.

    PubMed

    Dewall, Ryan J

    2013-01-01

    Ultrasound elastography is an emerging set of imaging modalities used to image tissue elasticity and are often referred to as virtual palpation. These techniques have proven effective in detecting and assessing many different pathologies, because tissue mechanical changes often correlate with tissue pathological changes. This article reviews the principles of ultrasound elastography, many of the ultrasound-based techniques, and popular clinical applications. Originally, elastography was a technique that imaged tissue strain by comparing pre- and postcompression ultrasound images. However, new techniques have been developed that use different excitation methods such as external vibration or acoustic radiation force. Some techniques track transient phenomena such as shear waves to quantitatively measure tissue elasticity. Clinical use of elastography is increasing, with applications including lesion detection and classification, fibrosis staging, treatment monitoring, vascular imaging, and musculoskeletal applications. PMID:23510006

  13. imaging of the Herschel Reference Survey. The star formation properties of a volume-limited, K-band-selected sample of nearby late-type galaxies

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Fossati, M.; Gavazzi, G.; Ciesla, L.; Buat, V.; Boissier, S.; Hughes, T. M.

    2015-07-01

    We present new Hα+[NII] imaging data of late-type galaxies in the Herschel Reference Survey aimed at studying the star formation properties of a K-band-selected, volume-limited sample of nearby galaxies. The Hα+[NII] data are corrected for [NII] contamination and dust attenuation using different recipes based on the Balmer decrement and the 24 μm luminosities. We show that the Hα luminosities derived with different corrections give consistent results only whenever the uncertainty on the estimate of the Balmer decrement is σ [C(Hβ)] ≤ 0.1. We used these data to derive the star formation rate of the late-type galaxies of the sample and compare these estimates to those determined using independent monochromatic tracers (far-UV, radio continuum) or the output of spectral energy distribution (SED) fitting codes. This comparison suggests that the 24 μm based dust extinction correction for the Hα data might not be universal and that it should be used with caution in all objects with a low star formation activity, where dust heating can be dominated by the old stellar population. Furthermore, because of the sudden truncation of the star formation activity of cluster galaxies occurring after their interaction with the surrounding environment, the stationarity conditions required to transform monochromatic fluxes into star formation rates might not always be satisfied in tracers other than the Hα luminosity. In a similar way, the parametrisation of the star formation history generally used in SED fitting codes might not be adequate for these recently interacting systems. We then use the derived star formation rates to study the star formation rate luminosity distribution and the typical scaling relations of the late-type galaxies of the HRS. We observe a systematic decrease of the specific star formation rate with increasing stellar mass, stellar mass surface density, and metallicity. We also observe an increase of the asymmetry and smoothness parameters measured

  14. The Idiom Principle Revisited

    ERIC Educational Resources Information Center

    Siyanova-Chanturia, Anna; Martinez, Ron

    2015-01-01

    John Sinclair's Idiom Principle famously posited that most texts are largely composed of multi-word expressions that "constitute single choices" in the mental lexicon. At the time that assertion was made, little actual psycholinguistic evidence existed in support of that holistic, "single choice," view of formulaic language. In…

  15. Reprographic Principles Made Easy.

    ERIC Educational Resources Information Center

    Young, J. B.

    Means for reproducing graphic materials are explained. There are several types of processes: those using light sensitive material, those using heat sensitive material, those using photo conductive materials (electrophotography), and duplicating processes using ink. For each of these, the principles behind them are explained, the necessary…

  16. PRINCIPLES OF WATER FILTRATION

    EPA Science Inventory

    This paper reviews principles involved in the processes commonly used to filter drinking water for public water systems. he most common approach is to chemically pretreat water and filter it through a deep (2-1/2 to 3 ft) bed of granuu1ar media (coal or sand or combinations of th...

  17. Extended Mach Principle.

    ERIC Educational Resources Information Center

    Rosen, Joe

    1981-01-01

    Discusses the meaning of symmetry of the laws of physics and symmetry of the universe and the connection between symmetries and asymmetries of the laws of physics and those of the universe. An explanation of Hamilton's principle is offered. The material is suitable for informal discussions with students. (Author/SK)

  18. Basic Comfort Heating Principles.

    ERIC Educational Resources Information Center

    Dempster, Chalmer T.

    The material in this beginning book for vocational students presents fundamental principles needed to understand the heating aspect of the sheet metal trade and supplies practical experience to the student so that he may become familiar with the process of determining heat loss for average structures. Six areas covered are: (1) Background…

  19. Matters of Principle.

    ERIC Educational Resources Information Center

    Martz, Carlton

    1999-01-01

    This issue of "Bill of Rights in Action" looks at individuals who have stood on principle against authority or popular opinion. The first article investigates John Adams and his defense of British soldiers at the Boston Massacre trials. The second article explores Archbishop Thomas Becket's fatal conflict with England's King Henry II. The final…

  20. Principles of Biomedical Ethics

    PubMed Central

    Athar, Shahid

    2012-01-01

    In this presentation, I will discuss the principles of biomedical and Islamic medical ethics and an interfaith perspective on end-of-life issues. I will also discuss three cases to exemplify some of the conflicts in ethical decision-making. PMID:23610498

  1. Fermat's Principle Revisited.

    ERIC Educational Resources Information Center

    Kamat, R. V.

    1991-01-01

    A principle is presented to show that, if the time of passage of light is expressible as a function of discrete variables, one may dispense with the more general method of the calculus of variations. The calculus of variations and the alternative are described. The phenomenon of mirage is discussed. (Author/KR)

  2. [Principles and juridical limits to human embryo research].

    PubMed

    de Sá, Maria de Fátima

    2003-01-01

    This work intends to provide a wide scope of the legal situation in Brazil referred to Human Embryos and how it has been developed through the 20th century. Across the last century, the human being got the possibility of making genetic experiments with human embryos. Our main goal is to assume the future responsibility of these actions through a juridical and ethical point of view. PMID:15032101

  3. Resolution limits of ultrafast ultrasound localization microscopy.

    PubMed

    Desailly, Yann; Pierre, Juliette; Couture, Olivier; Tanter, Mickael

    2015-11-21

    As in other imaging methods based on waves, the resolution of ultrasound imaging is limited by the wavelength. However, the diffraction-limit can be overcome by super-localizing single events from isolated sources. In recent years, we developed plane-wave ultrasound allowing frame rates up to 20,000 fps. Ultrafast processes such as rapid movement or disruption of ultrasound contrast agents (UCA) can thus be monitored, providing us with distinct punctual sources that could be localized beyond the diffraction limit. We previously showed experimentally that resolutions beyond λ/10 can be reached in ultrafast ultrasound localization microscopy (uULM) using a 128 transducer matrix in reception. Higher resolutions are theoretically achievable and the aim of this study is to predict the maximum resolution in uULM with respect to acquisition parameters (frequency, transducer geometry, sampling electronics). The accuracy of uULM is the error on the localization of a bubble, considered a point-source in a homogeneous medium. The proposed model consists in two steps: determining the timing accuracy of the microbubble echo in radiofrequency data, then transferring this time accuracy into spatial accuracy. The simplified model predicts a maximum resolution of 40 μm for a 1.75 MHz transducer matrix composed of two rows of 64 elements. Experimental confirmation of the model was performed by flowing microbubbles within a 60 μm microfluidic channel and localizing their blinking under ultrafast imaging (500 Hz frame rate). The experimental resolution, determined as the standard deviation in the positioning of the microbubbles, was predicted within 6 μm (13%) of the theoretical values and followed the analytical relationship with respect to the number of elements and depth. Understanding the underlying physical principles determining the resolution of superlocalization will allow the optimization of the imaging setup for each organ. Ultimately, accuracies better than the size of

  4. Qualitative biomechanical principles for application in coaching.

    PubMed

    Knudson, Duane

    2007-01-01

    Many aspects of human movements in sport can be readily understood by Newtonian rigid-body mechanics. Many of these laws and biomechanical principles, however, are counterintuitive to a lot of people. There are also several problems in the application of biomechanics to sports, so the application of biomechanics in the qualitative analysis of sport skills by many coaches has been limited. Biomechanics scholars have long been interested in developing principles that facilitate the qualitative application of biomechanics to improve movement performance and reduce the risk of injury. This paper summarizes the major North American efforts to establish a set of general biomechanical principles of movement, and illustrates how principles can be used to improve the application of biomechanics in the qualitative analysis of sport technique. A coach helping a player with a tennis serve is presented as an example. The standardization of terminology for biomechanical principles is proposed as an important first step in improving the application ofbiomechanics in sport. There is also a need for international cooperation and research on the effectiveness of applying biomechanical principles in the coaching of sport techniques. PMID:17542182

  5. CT Perfusion of the Liver: Principles and Applications in Oncology

    PubMed Central

    Kim, Se Hyung; Kamaya, Aya

    2014-01-01

    With the introduction of molecularly targeted chemotherapeutics, there is an increasing need for defining new response criteria for therapeutic success because use of morphologic imaging alone may not fully assess tumor response. Computed tomographic (CT) perfusion imaging of the liver provides functional information about the microcirculation of normal parenchyma and focal liver lesions and is a promising technique for assessing the efficacy of various anticancer treatments. CT perfusion also shows promising results for diagnosing primary or metastatic tumors, for predicting early response to anticancer treatments, and for monitoring tumor recurrence after therapy. Many of the limitations of early CT perfusion studies performed in the liver, such as limited coverage, motion artifacts, and high radiation dose of CT, are being addressed by recent technical advances. These include a wide area detector with or without volumetric spiral or shuttle modes, motion correction algorithms, and new CT reconstruction technologies such as iterative algorithms. Although several issues related to perfusion imaging—such as paucity of large multicenter trials, limited accessibility of perfusion software, and lack of standardization in methods—remain unsolved, CT perfusion has now reached technical maturity, allowing for its use in assessing tumor vascularity in larger-scale prospective clinical trials. In this review, basic principles, current acquisition protocols, and pharmacokinetic models used for CT perfusion imaging of the liver are described. Various oncologic applications of CT perfusion of the liver are discussed and current challenges, as well as possible solutions, for CT perfusion are presented. © RSNA, 2014 Online supplemental material is available for this article. PMID:25058132

  6. PET/CT: fundamental principles.

    PubMed

    Seemann, Marcus D

    2004-05-28

    Positron emission tomography (PET) facilitates the evaluation of metabolic and molecular characteristics of a wide variety of cancers, but is limited in its ability to visualize anatomical structures. Computed tomography (CT) facilitates the evaluation of anatomical structures of cancers, but can not visualize their metabolic and molecular aspects. Therefore, the combination of PET and CT provides the ability to accurately register metabolic and molecular aspects of disease with anatomical findings, adding further information to the diagnosis and staging of tumors. The recent generation of high performance PET/CT scanners combines a state of the art full-ring 3D PET scanner and a high-end 16-slice CT scanner. In PET/CT scanners, a CT examination is used for attenuation correction of PET images rather than standard transmission scanning using superset 68 Ge sources. This reduces the examination time, but metallic objects and contrast agents that alter the CT image quality and quantitative measurements of standardized uptake values (SUV) may lead to artifacts in the PET images. Hybrid PET/CT imaging will be very important in oncological applications in the decades to come, and possibly for use in cancer screening and cardiac imaging. PMID:15257877

  7. Medical photography: principles for orthopedics

    PubMed Central

    2014-01-01

    Background Medical photography is used clinically for patient evaluation, treatment decisions, and scientific documentation. Although standards for medical photography exist in many branches of medicine, we have not encountered such criteria in publications in the area of orthopedics. Purpose This study aims to (1) assess the quality of medical images used in an orthopedic publication and (2) to propose standards for medical photography in this area. Methods Clinical photographs were reviewed from all issues of a journal published between the years 2008 and 2012. A quality of clinical images was developed based on the criteria published for the specialties of dermatology and cosmetic surgery. All images were reviewed on the appropriateness of background, patient preparation, and technique. Results In this study, only 44.9% of clinical images in an orthopedic publication adhered to the proposed conventions. Conclusions Standards have not been established for medical photography in orthopedics as in other specialty areas. Our results suggest that photographic clinical information in orthopedic publications may be limited by inadequate presentation. We propose that formal conventions for clinical images should be established. PMID:24708703

  8. Aposematism and the handicap principle.

    PubMed

    Holen, Øistein Haugsten; Svennungsen, Thomas Owens

    2012-11-01

    Aposematic prey use conspicuous warning signals to advertise their defenses to predators. It has long been recognized that the efficiency of a warning signal may be reduced if poorly defended prey (automimics) are present in the population. The handicap principle suggests that the use of warning signals by poorly defended prey may be kept in check if signaling is costly. Three mechanisms that involve signal costs have been proposed to facilitate honest warning signals in prey: go-slow behavior in predators, resource allocation trade-offs, and costs of detection alone. We study all three in a unified game-theoretical framework. We find that the go-slow mechanism and the resource allocation mechanism can introduce differential benefits and differential costs of signaling, respectively, and can support honest signaling in accordance with the handicap principle. When honest signaling is maintained by the go-slow mechanism, conspicuous prey will necessarily suffer more attacks on average than cryptic prey. In contrast, when honest signaling is maintained by the resource allocation mechanism, cryptic prey will suffer more attacks. The detection cost mechanism lacks differential costs and benefits, and its potential for maintaining honest signaling equilibria is limited. We relate our results to intra- and interspecific correlations between conspicuousness and defense. PMID:23070323

  9. Diffraction-limited imaging with very large telescopes; Proceedings of the NATO Advanced Study Institute, Cargese, France, Sept. 13-23, 1988

    NASA Astrophysics Data System (ADS)

    Alloin, D. M.; Mariotti, J.-M.

    Recent advances in optics and observation techniques for very large astronomical telescopes are discussed in reviews and reports. Topics addressed include Fourier optics and coherence, optical propagation and image formation through a turbulent atmosphere, radio telescopes, continuously deformable telescopes for optical interferometry (I), amplitude estimation from speckle I, noise calibration of speckle imagery, and amplitude estimation from diluted-array I. Consideration is given to first-order imaging methods, speckle imaging with the PAPA detector and the Knox-Thompson algorithm, phase-closure imaging, real-time wavefront sensing and adaptive optics, differential I, astrophysical programs for high-angular-resolution optical I, cophasing telescope arrays, aperture synthesis for space observatories, and lunar occultations for marcsec resolution.

  10. Virtuous principles as an ethic for nursing.

    PubMed

    Tuckett, A G

    2000-06-01

    A theoretical analysis of virtuous principles--beneficence, non-maleficence, autonomy and justice provides a response to the question: 'How ought ethical nursing practice be characterised?' These virtuous principles promote human flourishing and sustain and strengthen nursing practice. Beneficence, described as acting to benefit others, incorporates a balance of benefit over harm and requires nurses to take action. Non-maleficence calls nurses to refrain from inflicting harm and defines prohibitions over actions. Autonomy, defined as self-governance and self-determination, may have limitations so that absolute or perfect autonomy might be unrealistic. Finally, Justice, a problematic concept, is aligned with fairness and what a patient deserves. PMID:11854998

  11. A geodesic principle for strong coupling gravity

    NASA Astrophysics Data System (ADS)

    Niedermaier, Max

    2015-11-01

    Strong coupling gravity arises from general relativity by a scaling limit that preserves the number of physical degrees of freedom as well as covariance under the group of spatio-temporal diffeomorphisms. An intrinsic geodesic principle for it is formulated and justified. Geodesic congruences and the test bodies following them are, according to the principle, unaffected by nonlinear gravitational waves and can be gauged-fixed so as to never depart from their initial values. Among other consequences this offers a new perspective on gravitational coarse graining.

  12. Common Principles and Multiculturalism

    PubMed Central

    Zahedi, Farzaneh; Larijani, Bagher

    2009-01-01

    Judgment on rightness and wrongness of beliefs and behaviors is a main issue in bioethics. Over centuries, big philosophers and ethicists have been discussing the suitable tools to determine which act is morally sound and which one is not. Emerging the contemporary bioethics in the West has resulted in a misconception that absolute westernized principles would be appropriate tools for ethical decision making in different cultures. We will discuss this issue by introducing a clinical case. Considering various cultural beliefs around the world, though it is not logical to consider all of them ethically acceptable, we can gather on some general fundamental principles instead of going to the extremes of relativism and absolutism. Islamic teachings, according to the presented evidence in this paper, fall in with this idea. PMID:23908720

  13. Digital deformation model for fisheye image rectification.

    PubMed

    Hou, Wenguang; Ding, Mingyue; Qin, Nannan; Lai, Xudong

    2012-09-24

    Fisheye lens can provide a wide view over 180°. It then has prominence advantages in three dimensional reconstruction and machine vision applications. However, the serious deformation in the image limits fisheye lens's usage. To overcome this obstacle, a new rectification method named DDM (Digital Deformation Model) is developed based on two dimensional perspective transformation. DDM is a type of digital grid representation of the deformation of each pixel on CCD chip which is built by interpolating the difference between the actual image coordinate and pseudo-ideal coordinate of each mark on a control panel. This method obtains the pseudo-ideal coordinate according to two dimensional perspective transformation by setting four mark's deformations on image. The main advantages are that this method does not rely on the optical principle of fisheye lens and has relatively less computation. In applications, equivalent pinhole images can be obtained after correcting fisheye lens images using DDM. PMID:23037373

  14. A correspondence principle

    NASA Astrophysics Data System (ADS)

    Hughes, Barry D.; Ninham, Barry W.

    2016-02-01

    A single mathematical theme underpins disparate physical phenomena in classical, quantum and statistical mechanical contexts. This mathematical "correspondence principle", a kind of wave-particle duality with glorious realizations in classical and modern mathematical analysis, embodies fundamental geometrical and physical order, and yet in some sense sits on the edge of chaos. Illustrative cases discussed are drawn from classical and anomalous diffusion, quantum mechanics of single particles and ideal gases, quasicrystals and Casimir forces.

  15. Pauli Exclusion Principle

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A principle of quantum theory, devised in 1925 by Wolfgang Pauli (1900-58), which states that no two fermions may exist in the same quantum state. The quantum state of a particle is defined by a set of numbers that describe quantities such as energy, angular momentum and spin. Fermions are particles such as quarks, protons, neutrons and electrons, that have spin = ½ (in units of h/2π, where h is ...

  16. Computational principles of memory.

    PubMed

    Chaudhuri, Rishidev; Fiete, Ila

    2016-03-01

    The ability to store and later use information is essential for a variety of adaptive behaviors, including integration, learning, generalization, prediction and inference. In this Review, we survey theoretical principles that can allow the brain to construct persistent states for memory. We identify requirements that a memory system must satisfy and analyze existing models and hypothesized biological substrates in light of these requirements. We also highlight open questions, theoretical puzzles and problems shared with computer science and information theory. PMID:26906506

  17. Principles of nuclear geology

    SciTech Connect

    Aswathanarayana, U.

    1985-01-01

    This book treats the basic principles of nuclear physics and the mineralogy, geochemistry, distribution and ore deposits of uranium and thorium. The application of nuclear methodology in radiogenic heat and thermal regime of the earth, radiometric prospecting, isotopic age dating, stable isotopes and cosmic-ray produced isotopes is covered. Geological processes, such as metamorphic chronology, petrogenesis, groundwater movement, and sedimentation rate are focussed on.

  18. Coded Access Optical Sensor (CAOS) Imager

    NASA Astrophysics Data System (ADS)

    Riza, N. A.; Amin, M. J.; La Torre, J. P.

    2015-04-01

    High spatial resolution, low inter-pixel crosstalk, high signal-to-noise ratio (SNR), adequate application dependent speed, economical and energy efficient design are common goals sought after for optical image sensors. In optical microscopy, overcoming the diffraction limit in spatial resolution has been achieved using materials chemistry, optimal wavelengths, precision optics and nanomotion-mechanics for pixel-by-pixel scanning. Imagers based on pixelated imaging devices such as CCD/CMOS sensors avoid pixel-by-pixel scanning as all sensor pixels operate in parallel, but these imagers are fundamentally limited by inter-pixel crosstalk, in particular with interspersed bright and dim light zones. In this paper, we propose an agile pixel imager sensor design platform called Coded Access Optical Sensor (CAOS) that can greatly alleviate the mentioned fundamental limitations, empowering smart optical imaging for particular environments. Specifically, this novel CAOS imager engages an application dependent electronically programmable agile pixel platform using hybrid space-time-frequency coded multiple-access of the sampled optical irradiance map. We demonstrate the foundational working principles of the first experimental electronically programmable CAOS imager using hybrid time-frequency multiple access sampling of a known high contrast laser beam irradiance test map, with the CAOS instrument based on a Texas Instruments (TI) Digital Micromirror Device (DMD). This CAOS instrument provides imaging data that exhibits 77 dB electrical SNR and the measured laser beam image irradiance specifications closely match (i.e., within 0.75% error) the laser manufacturer provided beam image irradiance radius numbers. The proposed CAOS imager can be deployed in many scientific and non-scientific applications where pixel agility via electronic programmability can pull out desired features in an irradiance map subject to the CAOS imaging operation.

  19. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  20. Principles of CT and CT technology.

    PubMed

    Goldman, Lee W

    2007-09-01

    This article provides a review of the basic principles of CT within the context of the evolution of CT. Modern CT technology can be understood as a natural progression of improvements and innovations in response to both engineering problems and clinical requirements. Detailed discussions of multislice CT, CT image quality evaluation, and radiation doses in CT will be presented in upcoming articles in this series. PMID:17823453

  1. Heisenberg's observability principle

    NASA Astrophysics Data System (ADS)

    Wolff, Johanna

    2014-02-01

    Werner Heisenberg's 1925 paper 'Quantum-theoretical re-interpretation of kinematic and mechanical relations' marks the beginning of quantum mechanics. Heisenberg famously claims that the paper is based on the idea that the new quantum mechanics should be 'founded exclusively upon relationships between quantities which in principle are observable'. My paper is an attempt to understand this observability principle, and to see whether its employment is philosophically defensible. Against interpretations of 'observability' along empiricist or positivist lines I argue that such readings are philosophically unsatisfying. Moreover, a careful comparison of Heisenberg's reinterpretation of classical kinematics with Einstein's argument against absolute simultaneity reveals that the positivist reading does not fit with Heisenberg's strategy in the paper. Instead the appeal to observability should be understood as a specific criticism of the causal inefficacy of orbital electron motion in Bohr's atomic model. I conclude that the tacit philosophical principle behind Heisenberg's argument is not a positivistic connection between observability and meaning, but the idea that a theory should not contain causally idle wheels.

  2. On limit and limit setting.

    PubMed

    Gorney, J E

    1994-01-01

    This article investigates the role of limit and limit setting within the psychoanalytic situation. Limit is understood to be a boundary between self and others, established as an interactional dimension of experience. Disorders of limit are here understood within the context of Winnicott's conception of the "anti-social tendency." Limit setting is proposed as a necessary and authentic response to the patient's acting out via holding and empathic responsiveness, viewed here as a form of boundary delineation. It is proposed that the patient attempts to repair his or her boundary problem through a seeking of secure limits within the analyst. The setting of secure and appropriate limits must arise from a working through of the analyst's own countertransference response to the patient. It is critical that this response be evoked by, and arise from, the immediate therapeutic interaction so that the patient can experience limit setting as simultaneously personal and authentic. PMID:7972580

  3. Principles and application of shock-tubes and shock tunnels

    NASA Technical Reports Server (NTRS)

    Ried, R. C.; Clauss, H. G., Jr.

    1963-01-01

    The principles, theoretical flow equations, calculation techniques, limitations and practical performance characteristics of basic and high performance shock tubes and shock tunnels are presented. Selected operating curves are included.

  4. The August Krogh principle applies to plants

    NASA Technical Reports Server (NTRS)

    Wayne, R.; Staves, M. P.

    1996-01-01

    The Krogh principle refers to the use of a large number of animals to study the large number of physiological problems, rather than limiting study to a particular organism for all problems. There may be organisms that are more suited to study of a particular problem than others. This same principle applies to plants. The authors are concerned with the recent trend in plant biology of using Arabidopsis thaliana as the "organism of choice." Arabidopsis is an excellent organism for molecular genetic research, but other plants are superior models for other research areas of plant biology. The authors present examples of the successful use of the Krogh principle in plant cell biology research, emphasizing the particular characteristics of the selected research organisms that make them the appropriate choice.

  5. Human perception of trademark images: implications for retrieval system design

    NASA Astrophysics Data System (ADS)

    Ren, Manling; Eakins, John P.; Briggs, Pamela

    2000-10-01

    A crucial aspect of shape similarity estimation is the identification of perceptually significant image elements. In order to understand more about the process of human segmentation of abstract images, a sample of 63 trademark images was shown to several groups of students in two experiments. Students were first presented with printed versions of a number of abstract trademark images, and invited to sketch their preferred segmentation of each image. A second group of students was then shown each image, plus its set of alternative segmentations, and invited to rank each alternative in order of preference. Our results suggest that most participants used a relatively small number of segmentation strategies, reflecting well-known psychological principles. Agreement between human image segmentations and those generated by the ARTISAN trademark retrieval system was quite limited; the most common causes of discrepancy were failure to handle texture and incorrect grouping of components into regions. Ways of improving ARTISAN's ability to model human segmentation behavior are discussed.

  6. Optimal Limited Contingency Planning

    NASA Technical Reports Server (NTRS)

    Meuleau, Nicolas; Smith, David E.

    2003-01-01

    For a given problem, the optimal Markov policy over a finite horizon is a conditional plan containing a potentially large number of branches. However, there are applications where it is desirable to strictly limit the number of decision points and branches in a plan. This raises the question of how one goes about finding optimal plans containing only a limited number of branches. In this paper, we present an any-time algorithm for optimal k-contingency planning. It is the first optimal algorithm for limited contingency planning that is not an explicit enumeration of possible contingent plans. By modelling the problem as a partially observable Markov decision process, it implements the Bellman optimality principle and prunes the solution space. We present experimental results of applying this algorithm to some simple test cases.

  7. Breaking the resolution limit: an exciting experimental result

    NASA Astrophysics Data System (ADS)

    Simonetti, Francesco

    2006-03-01

    For more than a century the possibility of imaging the structure of a medium with diffracting wavefields has been limited by the tradeoff between resolution and imaging depth. While long wavelengths can penetrate deep into a medium, the resolution limit precludes the possibility of observing subwavelength structures. Recent progress in microscopy has shown that by exploiting the super-oscillatory properties of evanescent fields, resolution several orders of magnitude smaller than the wavelength can be achieved so leading to Near-field Scanning Optical Microscopy. Based on a similar argument, this paper investigates the possibility of obtaining super resolution in the far-field (here far-field refers to a distance greater than λ, which would enable high resolution imaging at relatively large depth. The theoretical principles which result in the resolution limit are reviewed and a new strategy to overcome it is proposed. An advanced imaging algorithm for linear and two-dimensional array probing systems is presented and its capability of resolving targets as close as λ/3 is demonstrated experimentally, the targets being at several wavelength distance from the array. The results show that the method is superior to conventional techniques such as Synthetic Aperture Focusing, Synthetic Phased Arrays and Time Reversal.

  8. Image-based terrain modeling with thematic mapper applied to resolving the limit of Holocene Lake expansion in the Great Salt Lake Desert, Utah, part 1

    NASA Technical Reports Server (NTRS)

    Merola, John A.

    1989-01-01

    The LANDSAT Thematic Mapper (TM) scanner records reflected solar energy from the earth's surface in six wavelength regions, or bands, and one band that records emitted energy in the thermal region, giving a total of seven bands. Useful research was extracted about terrain morphometry from remote sensing measurements and this information is used in an image-based terrain model for selected coastal geomorphic features in the Great Salt Lake Desert (GSLD). Technical developments include the incorporation of Aerial Profiling of Terrain System (APTS) data in satellite image analysis, and the production and use of 3-D surface plots of TM reflectance data. Also included in the technical developments is the analysis of the ground control point spatial distribution and its affects on geometric correction, and the terrain mapping procedure; using satellite data in a way that eliminates the need to degrade the data by resampling. The most common approach for terrain mapping with multispectral scanner data includes the techniques of pattern recognition and image classification, as opposed to direct measurement of radiance for identification of terrain features. The research approach in this investigation was based on an understanding of the characteristics of reflected light resulting from the variations in moisture and geometry related to terrain as described by the physical laws of radiative transfer. The image-based terrain model provides quantitative information about the terrain morphometry based on the physical relationship between TM data, the physical character of the GSLD, and the APTS measurements.

  9. Indirect Imaging

    NASA Astrophysics Data System (ADS)

    Kundu, Mukul R.

    This book is the Proceedings of an International Symposium held in Sydney, Australia, August 30-September 2, 1983. The meeting was sponsored by the International Union of Radio Science and the International Astronomical Union.Indirect imaging is based upon the principle of determining the actual form of brightness distribution in a complex case by Fourier synthesis, using information derived from a large number of Fourier components. The main topic of the symposium was how to get the best images from data obtained from telescopes and other similar imaging instruments. Although the meeting was dominated by radio astronomers, with the consequent dominance of discussion of indirect imaging in the radio domain, there were quite a few participants from other disciplines. Thus there were some excellent discussions on optical imaging and medical imaging.

  10. Principles of tendon transfers.

    PubMed

    Coulet, B

    2016-04-01

    Tendon transfers are carried out to restore functional deficits by rerouting the remaining intact muscles. Transfers are highly attractive in the context of hand surgery because of the possibility of restoring the patient's ability to grip. In palsy cases, tendon transfers are only used when a neurological procedure is contraindicated or has failed. The strategy used to restore function follows a common set of principles, no matter the nature of the deficit. The first step is to clearly distinguish between deficient muscles and muscles that could be transferred. Next, the type of palsy will dictate the scope of the program and the complexity of the gripping movements that can be restored. Based on this reasoning, a surgical strategy that matches the means (transferable muscles) with the objectives (functions to restore) will be established and clearly explained to the patient. Every paralyzed hand can be described using three parameters. 1) Deficient segments: wrist, thumb and long fingers; 2) mechanical performance of muscles groups being revived: high energy-wrist extension and finger flexion that require strong transfers with long excursion; low energy-wrist flexion and finger extension movements that are less demanding mechanically, because they can be accomplished through gravity alone in some cases; 3) condition of the two primary motors in the hand: extrinsics (flexors and extensors) and intrinsics (facilitator). No matter the type of palsy, the transfer surgery follows the same technical principles: exposure, release, fixation, tensioning and rehabilitation. By performing an in-depth analysis of each case and by following strict technical principles, tendon transfer surgery leads to reproducible results; this allows the surgeon to establish clear objectives for the patient preoperatively. PMID:27117119

  11. Protection - Principles and practice.

    NASA Technical Reports Server (NTRS)

    Graham, G. S.; Denning, P. J.

    1972-01-01

    The protection mechanisms of computer systems control the access to objects, especially information objects. The principles of protection system design are formalized as a model (theory) of protection. Each process has a unique identification number which is attached by the system to each access attempted by the process. Details of system implementation are discussed, taking into account the storing of the access matrix, aspects of efficiency, and the selection of subjects and objects. Two systems which have protection features incorporating all the elements of the model are described.

  12. The principle of reciprocity.

    PubMed

    Hoult, D I

    2011-12-01

    The circumstances surrounding the realisation that NMR signal reception could be quantified in a simple fundamental manner using Lorentz's Principle of Reciprocity are described. The poor signal-to-noise ratio of the first European superconducting magnet is identified as a major motivating factor, together with the author's need to understand phenomena at a basic level. A summary is then given of the thought processes leading to the very simple pseudo-static formula that has been the basis of signal-to-noise calculations for over a generation. PMID:21889377

  13. Talus fractures: surgical principles.

    PubMed

    Rush, Shannon M; Jennings, Meagan; Hamilton, Graham A

    2009-01-01

    Surgical treatment of talus fractures can challenge even the most skilled foot and ankle surgeon. Complicated fracture patterns combined with joint dislocation of variable degrees require accurate assessment, sound understanding of principles of fracture care, and broad command of internal fixation techniques needed for successful surgical care. Elimination of unnecessary soft tissue dissection, a low threshold for surgical reduction, liberal use of malleolar osteotomy to expose body fracture, and detailed attention to fracture reduction and joint alignment are critical to the success of treatment. Even with the best surgical care complications are common and seem to correlate with injury severity and open injuries. PMID:19121756

  14. Nonequilibrium quantum Landauer principle.

    PubMed

    Goold, John; Paternostro, Mauro; Modi, Kavan

    2015-02-13

    Using the operational framework of completely positive, trace preserving operations and thermodynamic fluctuation relations, we derive a lower bound for the heat exchange in a Landauer erasure process on a quantum system. Our bound comes from a nonphenomenological derivation of the Landauer principle which holds for generic nonequilibrium dynamics. Furthermore, the bound depends on the nonunitality of dynamics, giving it a physical significance that differs from other derivations. We apply our framework to the model of a spin-1/2 system coupled to an interacting spin chain at finite temperature. PMID:25723198

  15. Principles of smile design

    PubMed Central

    Bhuvaneswaran, Mohan

    2010-01-01

    An organized and systematic approach is required to evaluate, diagnose and resolve esthetic problems predictably. It is of prime importance that the final result is not dependent only on the looks alone. Our ultimate goal as clinicians is to achieve pleasing composition in the smile by creating an arrangement of various esthetic elements. This article reviews the various principles that govern the art of smile designing. The literature search was done using PubMed search and Medline. This article will provide a basic knowledge to the reader to bring out a functional stable smile. PMID:21217950

  16. Prostatic carcinoma: limited field irradiation

    SciTech Connect

    Rounsaville, M.C.; Green, J.P.; Vaeth, J.M.; Purdon, R.P.; Heltzel, M.M.

    1987-07-01

    This is a retrospective study of 251 patients with histologically proven adenocarcinoma treated primarily with limited field radiotherapy techniques, under the principle direction of authors JMV and JPG, between 1968 and 1981 in San Francisco, California. All patients are followed for a minimum of 3 years; mean follow-up is 7.3 years. Routine clinical staging procedures included: HandP, digital prostate exam, cystoscopy, biopsy, blood studies including serum acid phosphatase, and imaging studies including chest X ray, IVP, bone survey or radionucleotide bone scan, and in recent years, pelvic CT scans. Twelve patients are Stage A1, 37-Stage A2, 50-Stage B, 140-Stage C1 and 12-Stage C2. Ninety percent of all cases and 85% of Stage C patients were treated with limited fields to the prostate and periprostatic volume only. Total doses were prescribed at midplane or isocenter and were generally 6500-7000 cGy, daily doses of 180-200 cGy, 5 days per week. Actuarial 5- and 10-year survival rates are: entire population-69% and 47%; Stage A1-74% and 50%; Stage A2-81% and 67%; Stage B-84% and 53%; Stage C1-63% and 42%; Stage C2-32% and 11%. The 5- and 10-year disease-free actuarial survivals are: entire population-71% and 50%; Stage A1-89% and 74%; Stage A2-82% and 69%; Stage B-71% and 52%; Stage C1-67% and 44%; Stage C2-0%. Sites of recurrence, alone or as a component of the failure pattern are: 37 (15%) local, 11 (4%) symptomatic regional recurrence (lower extremity edema, pelvic pain/sciatica, hydroureteronephrosis), and 87 (35%) distant metastasis. Seven (3%) had unknown sites of failure. Local-regional failure occurred in 42% of Stage C2 patients.

  17. Academic Principles: A Brief Introduction

    ERIC Educational Resources Information Center

    Association of American Universities, 2013

    2013-01-01

    For many decades certain core principles have guided the conduct of teaching, research, and scholarship at American universities, as well as the ways in which these institutions are governed. There is ample evidence that these principles have strongly contributed to the quality of American universities. The principles have also made these…

  18. Archimedes' Principle in General Coordinates

    ERIC Educational Resources Information Center

    Ridgely, Charles T.

    2010-01-01

    Archimedes' principle is well known to state that a body submerged in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body. Herein, Archimedes' principle is derived from first principles by using conservation of the stress-energy-momentum tensor in general coordinates. The resulting expression for the force is…

  19. Principles of climate service development

    NASA Astrophysics Data System (ADS)

    Buontempo, Carlo; Liggins, Felicity; Newton, Paula

    2015-04-01

    In November 2014, a group of 30 international experts in climate service development gathered in Honiton, UK, to discuss and identify the key principles that should be considered when developing new climate services by all the actors involved. Through an interactive and dynamic workshop the attendees identified seven principles. This contribution summarises these principles.

  20. Management Principles for Nonproliferation Organizations

    SciTech Connect

    Frazar, Sarah L.; Hund, Gretchen

    2012-03-06

    This paper identifies business models and six management principles that can be applied by a nonproliferation organization to maximize the value and effectiveness of its products. The organizations responsible for reducing the nuclear proliferation threat have experienced a substantial growth in responsibility and visibility since the September 11 attacks. Since then, the international community has witnessed revelations of clandestine nuclear facilities, nuclear black markets, periodic nuclear tests, and a resurgence of interest by countries worldwide in developing nuclear capabilities. The security environment will likely continue to evolve in unexpected ways since most of the proliferation threats with which the world will be forced to contend remain unforeseen. To better prepare for and respond to this evolving security environment, many nonproliferation organizations are interested in finding new or better ways to increase the effectiveness and efficiency of their operations. Of course, all organizations, whether they are market driven or non-profit, must operate effectively and efficiently if they are to succeed. Indeed, as this study demonstrates, many of the management principles that this study recommends can help all organizations succeed. However, this study pays particular attention to nonproliferation organizations because of the mission they are responsible for fulfilling. Nonproliferation organizations, including nonproliferation programs that operate within a larger national security organization, are responsible for reducing the threat of nuclear, chemical and biological weapons. These organizations have an enduring mandate from the public and the international community not to fail in the completion of their mission for failure could have detrimental impacts on international security, public health and the environment. Moreover, the public expects nonproliferation organizations and programs to fulfill their mission, even when resources are limited

  1. A test of the Copernican principle.

    PubMed

    Caldwell, R R; Stebbins, A

    2008-05-16

    The blackbody nature of the cosmic microwave background (CMB) radiation spectrum is used in a modern test of the Copernican principle. The reionized universe serves as a mirror to reflect CMB photons, thereby permitting a view of ourselves and the local gravitational potential. By comparing with measurements of the CMB spectrum, a limit is placed on the possibility that we occupy a privileged location, residing at the center of a large void. The Hubble diagram inferred from lines of sight originating at the center of the void may be misinterpreted to indicate cosmic acceleration. Current limits on spectral distortions are shown to exclude the largest voids which mimic cosmic acceleration. More sensitive measurements of the CMB spectrum could prove the existence of such a void or confirm the validity of the Copernican principle. PMID:18518434

  2. [Advance in imaging spectropolarimeter].

    PubMed

    Wang, Xin-quan; Xiangli, Bin; Huang, Min; Hu, Liang; Zhou, Jin-song; Jing, Juan-juan

    2011-07-01

    Imaging spectropolarimeter (ISP) is a type of novel photoelectric sensor which integrated the functions of imaging, spectrometry and polarimetry. In the present paper, the concept of the ISP is introduced, and the advances in ISP at home and abroad in recent years is reviewed. The principles of ISPs based on novel devices, such as acousto-optic tunable filter (AOTF) and liquid crystal tunable filter (LCTF), are illustrated. In addition, the principles of ISPs developed by adding polarized components to the dispersing-type imaging spectrometer, spatially modulated Fourier transform imaging spectrometer, and computer tomography imaging spectrometer are introduced. Moreover, the trends of ISP are discussed too. PMID:21942063

  3. Principles of Safety Pharmacology

    PubMed Central

    Pugsley, M K; Authier, S; Curtis, M J

    2008-01-01

    Safety Pharmacology is a rapidly developing discipline that uses the basic principles of pharmacology in a regulatory-driven process to generate data to inform risk/benefit assessment. The aim of Safety Pharmacology is to characterize the pharmacodynamic/pharmacokinetic (PK/PD) relationship of a drug's adverse effects using continuously evolving methodology. Unlike toxicology, Safety Pharmacology includes within its remit a regulatory requirement to predict the risk of rare lethal events. This gives Safety Pharmacology its unique character. The key issues for Safety Pharmacology are detection of an adverse effect liability, projection of the data into safety margin calculation and finally clinical safety monitoring. This article sets out to explain the drivers for Safety Pharmacology so that the wider pharmacology community is better placed to understand the discipline. It concludes with a summary of principles that may help inform future resolution of unmet needs (especially establishing model validation for accurate risk assessment). Subsequent articles in this issue of the journal address specific aspects of Safety Pharmacology to explore the issues of model choice, the burden of proof and to highlight areas of intensive activity (such as testing for drug-induced rare event liability, and the challenge of testing the safety of so-called biologics (antibodies, gene therapy and so on.). PMID:18604233

  4. Revisiting Tversky's diagnosticity principle.

    PubMed

    Evers, Ellen R K; Lakens, Daniël

    2014-01-01

    Similarity is a fundamental concept in cognition. In 1977, Amos Tversky published a highly influential feature-based model of how people judge the similarity between objects. The model highlights the context-dependence of similarity judgments, and challenged geometric models of similarity. One of the context-dependent effects Tversky describes is the diagnosticity principle. The diagnosticity principle determines which features are used to cluster multiple objects into subgroups. Perceived similarity between items within clusters is expected to increase, while similarity between items in different clusters decreases. Here, we present two pre-registered replications of the studies on the diagnosticity effect reported in Tversky (1977). Additionally, one alternative mechanism that has been proposed to play a role in the original studies, an increase in the choice for distractor items (a substitution effect, see Medin et al., 1995), is examined. Our results replicate those found by Tversky (1977), revealing an average diagnosticity-effect of 4.75%. However, when we eliminate the possibility of substitution effects confounding the results, a meta-analysis of the data provides no indication of any remaining effect of diagnosticity. PMID:25161638

  5. Revisiting Tversky's diagnosticity principle

    PubMed Central

    Evers, Ellen R. K.; Lakens, Daniël

    2013-01-01

    Similarity is a fundamental concept in cognition. In 1977, Amos Tversky published a highly influential feature-based model of how people judge the similarity between objects. The model highlights the context-dependence of similarity judgments, and challenged geometric models of similarity. One of the context-dependent effects Tversky describes is the diagnosticity principle. The diagnosticity principle determines which features are used to cluster multiple objects into subgroups. Perceived similarity between items within clusters is expected to increase, while similarity between items in different clusters decreases. Here, we present two pre-registered replications of the studies on the diagnosticity effect reported in Tversky (1977). Additionally, one alternative mechanism that has been proposed to play a role in the original studies, an increase in the choice for distractor items (a substitution effect, see Medin et al., 1995), is examined. Our results replicate those found by Tversky (1977), revealing an average diagnosticity-effect of 4.75%. However, when we eliminate the possibility of substitution effects confounding the results, a meta-analysis of the data provides no indication of any remaining effect of diagnosticity. PMID:25161638

  6. Principles of cryopreservation by vitrification.

    PubMed

    Fahy, Gregory M; Wowk, Brian

    2015-01-01

    Vitrification is an alternative approach to cryopreservation that enables hydrated living cells to be cooled to cryogenic temperatures in the absence of ice. Vitrification simplifies and frequently improves cryopreservation because it eliminates mechanical injury from ice, eliminates the need to find optimal cooling and warming rates, eliminates the importance of differing optimal cooling and warming rates for cells in mixed cell type populations, eliminates the need to find a frequently imperfect compromise between solution effects injury and intracellular ice formation, and enables cooling to be rapid enough to "outrun" chilling injury, but it complicates the osmotic effects of adding and removing cryoprotective agents and introduces a greater risk of cryoprotectant toxicity during the addition and removal of cryoprotectants. Fortunately, a large number of remedies for the latter problem have been discovered over the past 30+ years, and the former problem can in most cases be eliminated or adequately controlled by careful attention to technique. Vitrification is therefore beginning to realize its potential for enabling the superior and convenient cryopreservation of most types of biological systems (including molecules, cells, tissues, organs, and even some whole organisms), and vitrification is even beginning to be recognized as a successful strategy of nature for surviving harsh environmental conditions. However, many investigators who employ vitrification or what they incorrectly imagine to be vitrification have only a rudimentary understanding of the basic principles of this relatively new and emerging approach to cryopreservation, and this often limits the practical results that can be achieved. A better understanding may therefore help to improve present results while pointing the way to new strategies that may be yet more successful in the future. To assist this understanding, this chapter describes the basic principles of vitrification and indicates the

  7. Principles of Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Landé, Alfred

    2013-10-01

    Preface; Introduction: 1. Observation and interpretation; 2. Difficulties of the classical theories; 3. The purpose of quantum theory; Part I. Elementary Theory of Observation (Principle of Complementarity): 4. Refraction in inhomogeneous media (force fields); 5. Scattering of charged rays; 6. Refraction and reflection at a plane; 7. Absolute values of momentum and wave length; 8. Double ray of matter diffracting light waves; 9. Double ray of matter diffracting photons; 10. Microscopic observation of ρ (x) and σ (p); 11. Complementarity; 12. Mathematical relation between ρ (x) and σ (p) for free particles; 13. General relation between ρ (q) and σ (p); 14. Crystals; 15. Transition density and transition probability; 16. Resultant values of physical functions; matrix elements; 17. Pulsating density; 18. General relation between ρ (t) and σ (є); 19. Transition density; matrix elements; Part II. The Principle of Uncertainty: 20. Optical observation of density in matter packets; 21. Distribution of momenta in matter packets; 22. Mathematical relation between ρ and σ; 23. Causality; 24. Uncertainty; 25. Uncertainty due to optical observation; 26. Dissipation of matter packets; rays in Wilson Chamber; 27. Density maximum in time; 28. Uncertainty of energy and time; 29. Compton effect; 30. Bothe-Geiger and Compton-Simon experiments; 31. Doppler effect; Raman effect; 32. Elementary bundles of rays; 33. Jeans' number of degrees of freedom; 34. Uncertainty of electromagnetic field components; Part III. The Principle of Interference and Schrödinger's equation: 35. Physical functions; 36. Interference of probabilities for p and q; 37. General interference of probabilities; 38. Differential equations for Ψp (q) and Xq (p); 39. Differential equation for фβ (q); 40. The general probability amplitude Φβ' (Q); 41. Point transformations; 42. General theorem of interference; 43. Conjugate variables; 44. Schrödinger's equation for conservative systems; 45. Schr

  8. Indirect detection of pulmonary nodule on low-pass filtered and original x-ray images during limited and unlimited display times

    NASA Astrophysics Data System (ADS)

    Pietrzyk, Mariusz W.; McEntee, Mark; Evanoff, Michael G.; Brennan, Patrick C.

    2012-02-01

    Aim: This study evaluates the assumption that global impression is created based on low spatial frequency components of posterior-anterior chest radiographs. Background: Expert radiologists precisely and rapidly allocate visual attention on pulmonary nodules chest radiographs. Moreover, the most frequent accurate decisions are produced in the shortest viewing time, thus, the first hundred milliseconds of image perception seems be crucial for correct interpretation. Medical image perception model assumes that during holistic analysis experts extract information based on low spatial frequency (SF) components and creates a mental map of suspicious location for further inspection. The global impression results in flagged regions for detailed inspection with foveal vision. Method: Nine chest experts and nine non-chest radiologists viewed two sets of randomly ordered chest radiographs under 2 timing conditions: (1) 300ms; (2) free search in unlimited time. The same radiographic cases of 25 normal and 25 abnormal digitalized chest films constituted two image sets: low-pass filtered and unfiltered. Subjects were asked to detect nodules and rank confidence level. MRMC ROC DBM analyses were conducted. Results: Experts had improved ROC AUC while high SF components are displayed (p=0.03) or while low SF components were viewed under unlimited time (p=0.02) compared with low SF 300mSec viewings. In contrast, non-chest radiologists showed no significant changes when high SF are displayed under flash conditions compared with free search or while low SF components were viewed under unlimited time compared with flash. Conclusion: The current medical image perception model accurately predicted performance for non-chest radiologists, however chest experts appear to benefit from high SF features during the global impression.

  9. X ray microcalorimeters: Principles and performance

    NASA Technical Reports Server (NTRS)

    Moseley, S. H.; Juda, M.; Kelley, R. L.; Mccammon, D.; Stahle, C. K.; Szymkowiak, A. E.; Zhang, J.

    1992-01-01

    Microcalorimeters operating at cryogenic temperatures can be excellent X-ray spectrometers. They simultaneously offer very high spectral resolving power and high efficiency. These attributes are important for X-ray astronomy where most sources have low fluxes and where high spectral resolution is essential for understanding the physics of the emitting regions. The principles of operation of these detectors, limits to their sensitivity, design considerations, techniques of fabrication, and their performance as X-ray spectrometers, are reviewed.

  10. PRINCIPLE OF INTERACTION REGION LOCAL CORRECTION

    SciTech Connect

    WEI,J.

    1999-09-07

    For hadron storage rings like the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), the machine performance at collision is usually limited by the field quality of the interaction region (IR) magnets. A robust local correction for the IR region is valuable in improving the dynamic aperture with practically achievable magnet field quality. The authors present in this paper the action-angle kick minimization principle on which the local IR correction for both RHIC and the LHC are based.

  11. Low Temperature Detectors: Principles and Applications

    SciTech Connect

    Hilton, G. C.

    2009-12-16

    Despite the added cost and complexity of operating at sub-Kelvin temperatures, there are many measurement applications where the sensitivity and precision provided by low temperature detectors greatly outweigh any disadvantages. As a result, low temperature detectors are now finding wide application for measurements ranging from cosmology to homeland defense. In this tutorial I will introduce the basic operating principles and fundamental performance limits of several types of low temperature detectors.

  12. Fundamental limits on EMC

    NASA Astrophysics Data System (ADS)

    Showers, R. M.; Lin, S.-Y.; Schulz, R. B.

    1981-02-01

    Both fundamental and state-of-the-art limits are treated with emphasis on the former. Fundamental limits result from both natural and man-made electromagnetic noise which then affect two basic ratios, signal-to-noise (S/N) and extraneous-input-to-noise (I/N). Tolerable S/N values are discussed for both digital and analog communications systems. These lead to tolerable signal-to-extraneous-input (S/I) ratios, again for digital and analog communications systems, as well as radar and sonar. State-of-the-art limits for transmitters include RF noise emission, spurious emissions, and intermodulation. Receiver limits include adjacent-channel interactions, image, IF, and other spurious responses, including cross modulation, intermodulation, and desensitization. Unintentional emitters and receivers are also discussed. Coupling limitations between undesired sources and receptors are considered from mechanisms including radiation, induction, and conduction.

  13. Pyroelectric energy conversion: optimization principles.

    PubMed

    Sebald, Gael; Lefeuvre, Elie; Guyomar, Daniel

    2008-03-01

    In the framework of microgenerators, we present in this paper the key points for energy harvesting from temperature using ferroelectric materials. Thermoelectric devices profit from temperature spatial gradients, whereas ferroelectric materials require temporal fluctuation of temperature, thus leading to different applications targets. Ferroelectric materials may harvest perfectly the available thermal energy whatever the materials properties (limited by Carnot conversion efficiency) whereas thermoelectric material's efficiency is limited by materials properties (ZT figure of merit). However, it is shown that the necessary electric fields for Carnot cycles are far beyond the breakdown limit of bulk ferroelectric materials. Thin films may be an excellent solution for rising up to ultra-high electric fields and outstanding efficiency. Different thermodynamic cycles are presented in the paper: principles, advantages, and drawbacks. Using the Carnot cycle, the harvested energy would be independent of materials properties. However, using more realistic cycles, the energy conversion effectiveness remains dependent on the materials properties as discussed in the paper. A particular coupling factor is defined to quantify and check the effectiveness of pyroelectric energy harvesting. It is defined similarly to an electromechanical coupling factor as k2=p2theta0/(epsilontheta33cE), where p, theta0, epsilontheta33, cE are pyroelectric coefficient, maximum working temperature, dielectric permittivity, and specific heat, respectively. The importance of the electrothermal coupling factor is shown and discussed as an energy harvesting figure of merit. It gives the effectiveness of all techniques of energy harvesting (except the Carnot cycle). It is finally shown that we could reach very high efficiency using 1110.75Pb(Mg1/3Nb2/3)-0.25PbTiO3 single crystals and synchronized switch harvesting on inductor (almost 50% of Carnot efficiency). Finally, practical implementation key

  14. System level electrochemical principles

    NASA Technical Reports Server (NTRS)

    Thaller, L. H.

    1985-01-01

    The traditional electrochemical storage concepts are difficult to translate into high power, high voltage multikilowatt storage systems. The increased use of electronics, and the use of electrochemical couples that minimize the difficulties associated with the corrective measures to reduce the cell to cell capacity dispersion were adopted by battery technology. Actively cooled bipolar concepts are described which represent some attractive alternative system concepts. They are projected to have higher energy densities lower volumes than current concepts. They should be easier to scale from one capacity to another and have a closer cell to cell capacity balance. These newer storage system concepts are easier to manage since they are designed to be a fully integrated battery. These ideas are referred to as system level electrochemistry. The hydrogen-oxygen regenerative fuel cells (RFC) is probably the best example of the integrated use of these principles.

  15. Principles of Induction Accelerators

    NASA Astrophysics Data System (ADS)

    Briggs*, Richard J.

    The basic concepts involved in induction accelerators are introduced in this chapter. The objective is to provide a foundation for the more detailed coverage of key technology elements and specific applications in the following chapters. A wide variety of induction accelerators are discussed in the following chapters, from the high current linear electron accelerator configurations that have been the main focus of the original developments, to circular configurations like the ion synchrotrons that are the subject of more recent research. The main focus in the present chapter is on the induction module containing the magnetic core that plays the role of a transformer in coupling the pulsed power from the modulator to the charged particle beam. This is the essential common element in all these induction accelerators, and an understanding of the basic processes involved in its operation is the main objective of this chapter. (See [1] for a useful and complementary presentation of the basic principles in induction linacs.)

  16. Kepler and Mach's Principle

    NASA Astrophysics Data System (ADS)

    Barbour, Julian

    The definitive ideas that led to the creation of general relativity crystallized in Einstein's thinking during 1912 while he was in Prague. At the centenary meeting held there to mark the breakthrough, I was asked to talk about earlier great work of relevance to dynamics done at Prague, above all by Kepler and Mach. The main topics covered in this chapter are: some little known but basic facts about the planetary motions; the conceptual framework and most important discoveries of Ptolemy and Copernicus; the complete change of concepts that Kepler introduced and their role in his discoveries; the significance of them in Newton's work; Mach's realization that Kepler's conceptual revolution needed further development to free Newton's conceptual world of the last vestiges of the purely geometrical Ptolemaic world view; and the precise formulation of Mach's principle required to place GR correctly in the line of conceptual and technical evolution that began with the ancient Greek astronomers.

  17. Dynamical principles in neuroscience

    SciTech Connect

    Rabinovich, Mikhail I.; Varona, Pablo; Selverston, Allen I.; Abarbanel, Henry D. I.

    2006-10-15

    Dynamical modeling of neural systems and brain functions has a history of success over the last half century. This includes, for example, the explanation and prediction of some features of neural rhythmic behaviors. Many interesting dynamical models of learning and memory based on physiological experiments have been suggested over the last two decades. Dynamical models even of consciousness now exist. Usually these models and results are based on traditional approaches and paradigms of nonlinear dynamics including dynamical chaos. Neural systems are, however, an unusual subject for nonlinear dynamics for several reasons: (i) Even the simplest neural network, with only a few neurons and synaptic connections, has an enormous number of variables and control parameters. These make neural systems adaptive and flexible, and are critical to their biological function. (ii) In contrast to traditional physical systems described by well-known basic principles, first principles governing the dynamics of neural systems are unknown. (iii) Many different neural systems exhibit similar dynamics despite having different architectures and different levels of complexity. (iv) The network architecture and connection strengths are usually not known in detail and therefore the dynamical analysis must, in some sense, be probabilistic. (v) Since nervous systems are able to organize behavior based on sensory inputs, the dynamical modeling of these systems has to explain the transformation of temporal information into combinatorial or combinatorial-temporal codes, and vice versa, for memory and recognition. In this review these problems are discussed in the context of addressing the stimulating questions: What can neuroscience learn from nonlinear dynamics, and what can nonlinear dynamics learn from neuroscience?.

  18. Fault Management Guiding Principles

    NASA Technical Reports Server (NTRS)

    Newhouse, Marilyn E.; Friberg, Kenneth H.; Fesq, Lorraine; Barley, Bryan

    2011-01-01

    Regardless of the mission type: deep space or low Earth orbit, robotic or human spaceflight, Fault Management (FM) is a critical aspect of NASA space missions. As the complexity of space missions grows, the complexity of supporting FM systems increase in turn. Data on recent NASA missions show that development of FM capabilities is a common driver for significant cost overruns late in the project development cycle. Efforts to understand the drivers behind these cost overruns, spearheaded by NASA's Science Mission Directorate (SMD), indicate that they are primarily caused by the growing complexity of FM systems and the lack of maturity of FM as an engineering discipline. NASA can and does develop FM systems that effectively protect mission functionality and assets. The cost growth results from a lack of FM planning and emphasis by project management, as well the maturity of FM as an engineering discipline, which lags behind the maturity of other engineering disciplines. As a step towards controlling the cost growth associated with FM development, SMD has commissioned a multi-institution team to develop a practitioner's handbook representing best practices for the end-to-end processes involved in engineering FM systems. While currently concentrating primarily on FM for science missions, the expectation is that this handbook will grow into a NASA-wide handbook, serving as a companion to the NASA Systems Engineering Handbook. This paper presents a snapshot of the principles that have been identified to guide FM development from cradle to grave. The principles range from considerations for integrating FM into the project and SE organizational structure, the relationship between FM designs and mission risk, and the use of the various tools of FM (e.g., redundancy) to meet the FM goal of protecting mission functionality and assets.

  19. Monte Carlo simulations of medical imaging modalities

    SciTech Connect

    Estes, G.P.

    1998-09-01

    Because continuous-energy Monte Carlo radiation transport calculations can be nearly exact simulations of physical reality (within data limitations, geometric approximations, transport algorithms, etc.), it follows that one should be able to closely approximate the results of many experiments from first-principles computations. This line of reasoning has led to various MCNP studies that involve simulations of medical imaging modalities and other visualization methods such as radiography, Anger camera, computerized tomography (CT) scans, and SABRINA particle track visualization. It is the intent of this paper to summarize some of these imaging simulations in the hope of stimulating further work, especially as computer power increases. Improved interpretation and prediction of medical images should ultimately lead to enhanced medical treatments. It is also reasonable to assume that such computations could be used to design new or more effective imaging instruments.

  20. Fundamental limit on accuracy in interferometry.

    PubMed

    Kafri, O

    1989-07-01

    We derive a golden rule to evaluate the limit on fringe resolution. The rule, which is derived from basic principles, takes into consideration the existence of mechanical vibration. We show that conventional interferometer systems are limited by the available vibration-isolation tables to approximately 1/1000 of a fringe. In principle, moiré deflectometry can yield a much better signal-to-noise ratio. PMID:19752926